But, Dr. Ruth said, "Young people are not going to stop having sex."

Or stop talking about it.

Indeed, after an address that drew a crowd big enough to fill Science Center B twice, Ruth was kept occupied with questions from the audience that ranged from tame to down-right tittilating.

One statistically inclined student wanted to know what the average penis size was, and if sizes "several standard deviations below" this mean were cause for concern.

"I'm asked that on every campus," said Dr. Ruth, "but I have never been asked about the standard deviation before."

But Westheimer wasn't left speechless.

"Penis size has nothing to do with the sexual satisfaction of a woman," she said, explaining that the vagina was like a "balloon" and could accommodate any size.

When asked if a woman's desire for anal sex was "normal," Westheimer said, "There is nothing in my way of thinking that is normal or not normal."

However, she suggested that those engaging in anal sex utilize necessary precautions against infection.

Among the precautions prescribed by Dr. Ruth was the use of condoms, which she said she heartily endorses.

And, Westheimer said, she doesn't have much respect for those avoid using condoms by arguing that they inhibit sexual pleasure.

"Sex is not between the waist and the knees," she said. "Sex takes place between your ears."

Westheimer took time out Monday night to praise a local Cambridge law requiring that condom machines be installed in restaurants.

Westheimer also lauded the Peer Contraceptive Counselors, who along with the UHS and Carter-Wallance, the makers of Trojan condoms, sponsored the speech.

However, in such non-professional groups, she said, the right training and the issue of confidentiality has to be stressed.

"You can't walk around bearing the problems of everyone else. You'll end up as short as me," said Westheimer, who stands under five feet tall.

Dr. Ruth, who recently produced several documentaries, said she doesn't foresee an end to her career as a sex therapist for the masses.

"The day I get bored by questions," she said, "that's it. I haven't seen a real competitor yet."

And when asked about future goals, Dr. Ruth said she definitely had her eyes set on Harvard.

Holding up a bib for the audience to see, the good doctor said that, when the time is right, she hopes to enroll her newborn grandson in the College.