When people say they "had sex," what transpired is anyone's guess. A new study from the Kinsey Institute at Indiana University found that no uniform consensus existed when a representative sample of 18- to 96-year-olds was asked what the term meant to them.

Is oral sex considered sex? It wasn't to around 30 percent of the study participants. How about anal sex? For around 20 percent of the participants, no. A surprising number of older men did not consider penile-vaginal intercourse to be sex. More than idle gossip, the answers to questions about sex can inform -- or misinform -- research, medical advice and health education efforts.

"Researchers, doctors, parents, sex educators should all be very careful and not assume that their own definition of sex is shared by the person they're talking to, be it a patient, a student, a child or study participant," said Brandon Hill, research associate at the Kinsey Institute.

The study, conducted in conjunction with the Rural Center for AIDS/STD Prevention in IU's School of Health, Physical Education and Recreation, delves deeper into a question first examined in 1999 -- in the midst of a presidential sex scandal where the definition of sex was an issue. Researchers from The Kinsey Institute asked college students what "had sex" meant to them, taking the approach, which was unique then, of polling the students on specific behaviors.

No consensus was found then, either. The new study, published in the international health journal "Sexual Health" in February, examined whether more information helped clarify matters -- study participants were asked about specific sexual behaviors and such qualifiers as whether orgasm was reached -- and researchers also wanted to involve a more representative audience, not just college students.

"Throwing the net wider, with a more representative sample, only made it more confusing and complicated," Hill said. "People were even less consistent across the board."

The study involved responses from 486 Indiana residents who took part in a telephone survey conducted by the Center for Survey Research at IU. Participants, mostly heterosexual, were asked, "Would you say you 'had sex' with someone if the most intimate behavior you engaged in was ...," followed by 14 behaviorally specific items. Here are some of the results:

Responses did not differ significantly overall for men and women. The study involved 204 men and 282 women.

95 percent of respondents would consider penile-vaginal intercourse (PVI) having had sex, but this rate drops to 89 percent if there is no ejaculation.

81 percent considered penile-anal intercourse having had sex, with the rate dropping to 77 percent for men in the youngest age group (18-29), 50 percent for men in the oldest age group (65 and up) and 67 percent for women in the oldest age group.

71 percent and 73 percent considered oral contact with a partner's genitals (OG), either performing or receiving, as having had sex.

Men in the youngest and oldest age groups were less likely to answer "yes" compared with the middle two age groups for when they performed OG.

Significantly fewer men in the oldest age group answered "yes" for PVI (77 percent).

Hill said it is common for a doctor, when seeing a patient with symptoms of sexually transmitted infections, to ask how many sexual partners the patient has or has had. The number will differ according to the patients' definitions of sex.

William L. Yarber, RCAP's senior director and co-author of the study, said its findings reaffirm the need to be specific about behaviors when talking about sex

"There's a vagueness of what sex is in our culture and media," Yarber said. "If people don't consider certain behaviors sex, they might not think sexual health messages about risk pertain to them. The AIDS epidemic has forced us to be much more specific about behaviors, as far as identifying specific behaviors that put people at risk instead of just sex in general. But there's still room for improvement."

Co-authors include lead author Stephanie A. Sanders, Kinsey Institute, Department of Gender Studies and RCAP at IU; Cynthia A. Graham, Kinsey Institute and RCAP at IU, Doctoral Course in Clinical Psychology at the University of Oxford; Richard A. Crosby, Kinsey Institute and RCAP at IU, Department of Health Behavior at the University of Kentucky; and Robin R. Milhausen, Kinsey Institute and RCAP at IU, Department of Family Relations and Applied Nutrition at the University of Guelph.

Yarber is professor in the departments of Applied Health Science and Gender Studies at IU and is a senior research fellow at the Kinsey Institute. Hill also is a researcher in the Department of Gender Studies at IU.