Condom use and its psychosocial correlates were investigated in a sample of 1,725 male and female vocational students (aged 15-21 years) in northern Thailand. Consistent condom use was relatively infrequent with all partner types (8.0% with recent steady partners, 28.5% with casual partners, and 30.7% with commercial sex partners), and only 24.3% reported condom use at first sex. These findings suggest that condom use, even with commercial partners, is not becoming widely established in the younger generation of Thai youths. Condom use with commercial partners was far below goals established by Thailand's 100% Condom Campaign, which was particularly significant for a population in Thailand's HIV epicenter. Consistent condom use with a steady partner was significantly related to condom use during first sex, which suggests the importance of establishing a "condom habit." Consistent condom use with casual partners was related to never having been pregnant (self or partner). Having used condoms at first sex also was associated with never having been pregnant (self or partner), as well as with a number of background social and psychological factors. Intentions to use condom were highly related to peer norms. Results suggest the importance of addressing peer norms concerning condom use, as well as the role of condoms in effective birth control.