Objective. The aim of this study was to prospectively compare pregnant and nonpregnant adolescents' recent condom use and sexually transmitted disease (STD) acquisition. Methods. Sexually active African-American females (N = 522), ages 14-18, were recruited from clinics and schools. Adolescents completed baseline interviews and provided vaginal swabs for STD testing, and urine for pregnancy testing. Assessments were repeated 6 and 12 months post baseline assessment. Analyses compared adolescents who became pregnant between baseline and the 6-month assessment with their peers who had negative pregnancy tests. Condom use between the 6- and 12-month assessments and incidence of STDs at the 12-month assessment served as outcomes. Adolescents who did not report sexual activity between the 6- and 12-month assessments were excluded. Results. Ten percent of the adolescents became pregnant and continued sexual activity. Pregnant adolescents reported less overall condom use (P < 0.0001), more infrequent condom use (adjusted odds ratio [AOR] = 4.5, P < 0.001), and more unprotected vaginal sex (AOR = 4.7, P < 0.003). Pregnant adolescents were equally likely to test positive for STDs (31% vs 26%) and to self-report having STDs at the 12-month follow-up period (30% vs 23%). Conclusions. Findings suggest that pregnant adolescents may be less likely to use condoms than their nonpregnant peers and that STD incidence among pregnant adolescents may be high. Condom use promotion may be important during adolescents' prenatal care. © 2002 American Health Foundation and Elsevier Science (USA).