NEW YORK - The average American man has sex with seven women during his lifetime, compared with four male sexual partners for the average woman, according to a new federal survey that used high-tech methods to solicit candid answers on sexual activity and illegal drug use.

Men are far more apt to play the field when it comes to sex, the survey found; 29 percent of them reported having 15 or more female sexual partners in a lifetime, while 9 percent of women reported having sex with 15 or more men.

The survey, released yesterday, was based on data collected from 1999 to 2002 for the National Center for Health Statistics, a branch of the Centers for Disease Control and Prevention.

In previous federal surveys on those topics, participants were asked questions in face-to-face interviews; the CDC believes that caused underreporting of behaviors that might be viewed negatively.

This time, data were gathered from 6,237 adults, aged 20 to 59, in computer-assisted self-interviews.

"The participants have a headset on, they hear questions, they touch the screen with responses," said Kathryn Porter, medical officer for the survey. "There's no one else in the room and they can take as long as they want."

Though the survey results were presented by the CDC without subjective comment, they will likely provide ammunition to various parties in the national debate over sex education, cohabitation and access to birth control. The survey found about 11 percent of never-married adults had remained chaste.

Among the other findings:

About 96 percent of U.S. adults have had sex.

Sixteen percent of adults first had sex before age 15, while 15 percent abstained until at least age 21.

The proportion of adults who first had sex before age 15 was highest for non-Hispanic blacks (28 percent) compared with 14 percent for both Mexican Americans and non-Hispanic whites.

Six percent of blacks abstained from sex until age 21 or older, fewer than Mexican Americans (17 percent) or non-Hispanic whites (15 percent).

Twenty-five percent of women and 17 percent of men reported having one partner in their lifetime.

Twenty-six percent of men and 17 percent of women have tried cocaine or other street drugs, not including marijuana.

Adults who were married or had more than a high school education were less likely to use street drugs than others.