Effects were examined of a human immunodeficiency virus (HIV) prevention program for adolescent mothers offered in pregnant minor and parenting programs in Los Angeles County. The sample included young women (N = 497) of predominantly poor, Latina backgrounds who had complete data from baseline to the one-year follow-up. The treatment group demonstrated statistically significant improvements in AIDS knowledge and intentions to use condoms, and fewer sex partners at the six-month follow-up as compared to the control group. Findings related to the effects of the intervention on theoretical variables provide some support for selected concepts from Social Cognitive Theory and the Theory of Reasoned Action.