There is an understanding that effective HJV / AIDS prevention programs should be based on thernmodels and theories of behavior change so that the programs can be designed to change thosernfactors which lead to the Lmdesirable risk behaviors and maintain the desirable once. With thernobjectives of determining HIV / AIDS related sex ual behaviors and assessing their relation withrnvariables derived from the classical models of health behavior, a study using a pre-tested selfadministeredrnquestiOlUlaire to collect information from a random sample of six hundred and sixtyrnhigh school students was conducted in Jimma town on March 2000. Among the high schoolrnstudents 6.7% of female students and I 1.2% of male students were found to have involved inrnsexual activity with worst lifetime sexual behavior index. Of the sexually active students the raternof unprotected sexual intercourse and intercourse with more than one sexual pminer in the pastrnyear were 81. 7% and 19.3%, respectively.rnThere is a significant gender difference in HIV -related risk sexual act and belief-intention factors.rnHigher propOliions of males were involved in these high-risk sexual acts. Independent andrnsignificant predictors of intention to limit sexual paltners were perceived barriers and normativernbelief for female students and normative belief and perceived behavioral control for malernstudents. On the other hand, knowing an individual who has/had HIV / AIDS, motivation torncomply, normative belief, and perceived behavioral conh'ol for females; while only perceivedrnsusceptibility and perceived behavioral control for males independently and significantlyrnpredicted the intention to use condom in the next sexual intercourse. It was concluded that highrnschool students are at risk of HIV infection because of the high-risk behaviors they have. Pattemsrnof gender difference are found and theOly-driven and gender appropriate educationalrninterventions and researches are recommended.rnii