Bisexual high school males report high levels of unprotected sex and other behaviour that puts them at risk for HIV and other sexually transmitted diseases (STDs), according to a new study.

One of the factors that may account for this is the fact that gay and bisexual young men receive less HIV and AIDS education at school, according to the study.

"School AIDS education and condom instruction predicted less AIDS-related risk," according to the researchers.

Bisexually active youth also had more sexual partners -- they were almost three times as likely as heterosexual youths to have had sexual intercourse with four or more people. They were also more likely to have unprotected intercourse, an STD, and to use injection drugs.

Survey data was analysed from 3,065 males with only female sexual partners, 94 with only male partners and 108 with both male and female partners. The sample was taken from the 1995, 1997, or 1999 Massachusetts Youth Risk Behaviour Survey (MYRBS), which was completed by high school students.

"Understanding and preventing HIV/AIDS among young men who have sex with men (YMSM) represents a critical aspect of stemming the AIDS epidemic in the United States," according to the study authors. Yet 20 years into the epidemic there is very little research in this area, researchers warn.

"School-based AIDS prevention should address the needs of all sexually active youths," according to the study authors.

Findings were published in the February issue of the American Journal of Public Health.