This study examined the extent to which acculturation status in 141 pregnant Mexican American adolescents was associated with family and social support variables, sociodemographic profiles, cigarette smoking, substance abuse, and previous adverse pregnancy outcomes, Results indicated that highly acculturated females were more likely to have smoked cigarettes, taken illegal substances, drunk alcohol, and experienced a previous fetal or postnatal death. For the family variables, in turn, highly acculturated adolescents demonstrated greater stress levels resulting from the assimilation process, used more coping strategies, and had greater support given by family, friends, and relatives, This study underscores the importance of acculturation and its consequences for several medical and psychosocial health issues within a sample of Mexican American female adolescents from low-income backgrounds.