WASHINGTON (AP)—Most Americans are monogamous, but a significant minority engages in high-risk behavior by having multiple partners without always using condoms, according to a new survey.

The study, published this week in the American Journal of Public Health, said most sexually active Americans ‘‘are not placing themselves or their partners at high risk for exposure to HIV through sex with multiple partners.’‘

HIV is the virus that causes AIDS.

Barbara Leigh of the University of Washington in Seattle, an author of the study, said the survey shows, ‘‘There is an awful lot of monogamy going on out there.’‘

Also, she said, those who reported having more than one sex partner in the previous year were more likely to use a condom for sex with a casual partner than a primary partner.

‘‘That’s encouraging,’‘ she said.

The report said, ‘‘Having multiple sexual partners over a certain time period does not necessarily imply infidelity.’‘

It said those people likely are practicing ‘‘serial monogamy,’‘ being sexually faithful to each partner in turn.

Of those who said they had more than one partner in the previous 12 months, 85 percent said all their partners were either spouses or someone to whom they felt committed. Only 4 percent of the married people reported having more than one partner in the last year.

Also, the report said, ‘‘Although people rarely use condoms with primary partners, they are somewhat more likely to use condoms with casual partners.’‘

Among those who had more than one sexual partner in the previous year, only 8 percent said they used condoms every time they had sex. But 23 percent said they used a condom every time with their non-primary partners.

The higher risk group was made up mainly of people between 18 and 30, the divorced and those never married.

Only 2 percent of those responding identified themselves as homosexual or bisexual, a figure the authors said is consistent with a 1970 Kinsey survey.

The survey was conducted in 1990, and 2,058 people over the age of 18 responded. They were asked to complete a 20-page questionnaire and were paid $10 apiece.