Since low-income women are at increased risk of having low birth weight infants, factors associated with birth weight among such groups have special relevance. Cigarette-smoking has emerged as an important predictor of low birth weight due to intrauterine growth retardation and pre-term delivery. After confirming the relation of smoking with birth weight, we examined the association of smoking with sociodemographic factors, attitudes towards pregnancy, health behaviors, stressful life events, social support, and symptoms of mental distress in a cohort of 458 Central Harlem women. We found that social support, stress and mental health were associated with smoking behavior but not directly with birth weight. These findings suggest that programs designed to modify health behaviors such as smoking during pregnancy must also take into account such characteristics of the women and their environments which may make behavioral change difficult. Moreover, programs aimed at fostering better health behaviors to improve pregnancy outcome may have to extend beyond the current pregnancy, as indicated by an association between prior adverse pregnancy outcome and smoking in the current pregnancy.