DEAR ABBY: Would you please do all the parents of small children (babies especially) a big favor and tell the manufacturers of infant and toddler clothing to stop labeling the clothes by age (3 to 6 months, 18 months, etc.)? Nothing could be more irrelevant.

Our 4-month-old son is in the 95th percentile for length and weight for his age group. His clothes labels read 12 and 18 months. His pediatrician says he is in all respects normal -- just big (every bit of 21 pounds).

If clothes were labeled by weight and/or length, making an appropriate purchase without trying to wriggle an overtired infant into the outfit first might be possible. As it is, I have drawers full of sweatsuits given to my baby by well-meaning friends who thought they'd be just right for next winter since the label reads "12 months." Most of these clothes fit him now.

We live in Florida and the thermometer hit 90 degrees yesterday. What a shame. Had the clothes been labeled according to weight, since he was 9 1/2 pounds at birth, most people could have guessed he'd be at least three or four times that size a year later. I imagine parents of "preemies" have similar problems -- PAT IN ST. PETE

DEAR PAT: Your suggestion makes sense. Let's hope the folks who manufacture infant and toddler clothing take note.

DEAR ABBY: My stepdaughter "Susie" and her husband, who live out of state and rarely communicate with us, came to visit us last year. Their visit was complicated by the fact that they invited another couple (whom we had never met) and their two children to join them. We made special sleeping accommodations and fed all six of them for several days.

I was ignored, talked down to and insulted by both Susie and her friend "Betsy" during the entire visit. Neither woman offered to help with the meals or dishes -- they just sat while I waited on them. When it was time for them to leave, neither Susie nor Betsy said goodbye or thank you. They simply disappeared into their van while I stood there with tears in my eyes and egg on my face!

Now, Susie is making plans to use our home as a stop-over for several days next year -- and she's bringing Betsy and family along. I told my husband that I could tolerate Susie and her husband if I had to, but I would not have Betsy and her family as houseguests again.

Abby, am I justified in my decision, and how should this be handled without offending my husband's family? -- FRUSTRATED IN FLORIDA

DEAR FRUSTRATED: You are indeed "justified" in your decision, and if any of your husband's family are offended, they need only be told that you do not wish to accommodate guests who come uninvited and leave without so much as a goodbye or thank-you.

By popular request, Abby shares more of her favorite prize-winning, easy-to-prepare recipes. To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: More Favorite Recipes by Dear Abby, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)

DEAR ABBY: My son got into serious trouble and is in jail right now. He is 19 and began getting into trouble with the law three years ago. He's close to his grandparents, who live out of state, and when he first got into trouble at age 16, I kept them in the dark about it as long as I could. They eventually found out, and I know they worried a lot.

My son stayed out of trouble for more than a year. He went to counseling for alcohol abuse and other problems. I realized he still had problems. But three days ago, he and a friend of his broke into someone's garage to steal and were caught. My heart broke once again. My son is now in county jail. I visited him there and managed to hold back my tears in front of him, but I cried all the way home.

Here's my problem: Should I tell my parents, who are 1,000 miles away, and cause them all this grief? My mother telephones every weekend to "check in." I didn't have the heart to tell her this Sunday. Do you think she has the right to know? She always asks about her grandsons and is especially close to this one. I just don't want her to worry. -- BROKENHEARTED MOTHER

DEAR BROKENHEARTED: Since your mother always asks, and feels especially close to this grandchild, I think you should tell her the truth now. Eventually she will have to be told, unless you intend to deceive your parents about the boy's whereabouts until he's served his time. If so, your chances for pulling it off are slim.

DEAR ABBY: Please discuss fathers tickling their young children. They seem to get some sadistic pleasure out of expressing their love (?) by tickling the little girls and boys until they scream with laughter, then pain -- then end up in tears!

This needs discussion, Abby. I think it's sadistic! Do you? -- MRS. B. IN JOPLIN, MO.

DEAR MRS. B: Yes. Children who "end up in tears" are experiencing pain -- not pleasure -- and no father should be permitted to play such games. Excessive tickling is said to stimulate children inappropriately. To subject a child to this kind of "play" is child abuse. It's the business of adults to protect children from ANY kind of child abuse -- and while it may appear innocent and "all in fun," it should not be tolerated.

DEAR ABBY: The woman who was upset because her husband's friend held his fork incorrectly just about sent me through the roof. I wish all I had to worry about was how my friends held their dinner forks.

I'd like to tell that woman that if more people would hold their forks in their fists like a 3-year-old child, but were smart, college-educated, well-mannered and had great personalities, our country would be much better off.

I suppose a man could be a rapist, murderer or drug dealer, but as long as he held his dinner fork properly, he'd be OK? That woman should come down from her pedestal and start dealing with issues like world peace, abused children, caring for the elderly, and feeding the homeless -- who would be happy just to eat, let alone hold a fork properly! -- S.B., ROSEBURG, ORE.

Abby's family recipes are included in her cookbooklet. Send a long, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Cookbooklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)

DEAR ABBY: I am writing this from a well-known cancer and tumor clinic in Texas.

We are here because my husband, who has had a complete physical every year since 1971, has inoperable prostate cancer. I am angry and bitter because no doctor, during 20 years of annual physical examinations that included a digital rectal examination, ever mentioned that there are blood tests which can detect prostate cancer.

We have been told that my husband has had this disease for at least seven to eight years. We also learned that if a man's brother or father has had prostate cancer, his chances of getting cancer are increased 2 1/2 times! In every medical questionnaire my husband has ever filled out, he stated that his father had died of prostatic cancer. (His brother was diagnosed last week with the same disease!)

We are hoping that our experience will educate others so they will not find themselves where we are. We strongly urge all "high risk" men to be examined by a urologist, because many physicians do not recognize prostate disease. -- ANGRY AND BITTER

DEAR ANGRY AND BITTER: You have every right to be both angry and bitter, and I thank you for trying to warn others.

For readers who do not know what "high risk" means in this context, it refers to people whose blood relatives have been afflicted with the same disease.

DEAR ABBY: When a couple asks another couple to ride along with them, what is the proper seating? Should the wife automatically sit in front with her husband, or should she sit in the back with the other lady? Or should the couple whose car it is ask the other couple how they prefer to ride? -- EDNA C. IN CARMAN, ILL.

DEAR EDNA: It depends on the circumstances -- how well the couples know each other, the distance to be traveled and whether either of the couples are newlyweds. (Newlyweds usually prefer to sit together.)

The important factor in the seating arrangement is that everybody be pleased and comfortable. Couples who have a long friendship might prefer "one-on-one" conversation with the spouse of the same sex. My personal rule of thumb: When in doubt, sit with your own mate.

DEAR ABBY: Thank you for insisting that a written thank-you note for a gift is still absolutely imperative. I was appalled when a reader suggested that a "warm hug and a verbal thank-you at the next chance meeting at church or a social function should be sufficient."

A child should be taught at a very early age to write a thank-you note. Writing improves finger coordination, penmanship and spelling, and helps to create a bond between the child and the giver.

In today's world of electronic communication -- the telephone and fax -- it is still necessary to record thoughts, events and instructions in writing. If a "tape" is erased, the message is lost forever. Therefore it is vital that we learn how to communicate in writing. And it all begins when a child is taught to write a thank-you note.

At 86, I am still writing. -- M.S.P., SANTA ANA, CALIF.

To get Abby's booklet "How to Write Letters for All Occasions," send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Letter Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)