Wendy Strong, director of corporate communications for Kimberly-Clark, said the company's own marketing research confirmed that toddlers were toilet training later than in the past: only 12 percent of children are trained at 18 months, the company found, and 85 percent by 30 months. Huggies, too, just began offering customers a size-6 diaper, but the company also makes ''training pants'' for toddlers of 38 pounds or more, a product category, Ms. Strong said, that Kimberly-Clark ''expects to grow to more than a billion dollars by 2002.''

Whichever expert's school of parenting a toddler's parents decide to follow, they run no risk of confusing the philosophies, or the methods themselves.

Mr. Rosemond offers a toilet-training technique he calls ''naked and $75,'' which he recommends that parents embark upon with their 2-year-olds.

''You stay home from work with your child for a few days,'' he said, and ''you let the child walk around the house naked all day long.'' The parent puts the potty where the child spends most of his time, and moves it when necessary to keep it nearby. Every so often, the parent reminds the child to use the potty when needed.

''Children at this age do not like urine and feces running down their legs,'' Mr. Rosemond said. ''When they have an accident, they stop and start to howl, and the mother comes along and says, 'Well, you forgot to use the toilet.' She puts him on the toilet, wipes him off, speaks reassuringly to him. And within three days, or five days, he's doing it on his own.''

The $75, he added, is for the carpet cleaning.

In contrast, Dr. Brazelton, like Mr. Rosemond the author of best-selling parenting manuals, discourages parents from expecting their child to potty-train in a few days. He recommends that parents buy a potty chair and ''show children what is expected of them at 2, what we are all doing and why it is important.''

But, he says, the rate at which training occurs should be left up to the child.

''If your child is afraid of the potty chair, don't put pressure on him to use it,'' Dr. Brazelton advises in a step-by-step guide available on the Pampers Parenting Institute's Web site (www.pampers.com). ''Put toilet training aside for a month or two, and give your child time to get used to the idea of the potty and to be comfortable with it.''