This study assesses whether pregnant Mexican-American adolescents have psychosocial characteristics different from their pregnant white or black peers. The study population consisted of 199 consecutive Mexican-American, white, and black pregnant adolescents, ages 11-19 years, followed prospectively at the University of California San Diego Medical Center Teen Obstetric Clinic from 1978 to 1981 (79 whites, 76 Mexican-Americans, and 44 blacks). Although all three groups had the same chronologic age (X = 16.4 +/- 1.4 years), and the same number of years of schooling, pregnant black adolescents were more likely to be in school at the time of registration for prenatal care (p less than 0.01). Mexican-American teens were more likely to be married at conception and/or delivery (p less than 0.001), and to breastfeed their infants (p less than 0.05). The fathers of the Mexican-American babies were more likely than other fathers to be full-time students or employed (p less than 0.001). Although pregnant Mexican-American teens came from the largest families (p less than 0.001), black teenagers most frequently reported a good mother-daughter relationship (p less than 0.05). White pregnant teens most frequently reported a family history of psychiatric illness (p less than 0.01), parental death (p less than 0.05), or runaway behavior (p less than 0.01). These data suggest that pregnant teenagers from these three racial/ethnic backgrounds have different psychosocial profiles and hence different psychosocial problems and needs.