Randomized clinical trial to test the effects of a comprehensive prenatal, in-hospital, and postpartum education and support intervention on breastfeeding initiation and duration among teenage mothers. Experimental, attention control, and usual care groups are used to test the hypotheses. Drawing on the Theory of Planned Behavior and begun during the second trimester of pregnancy, the experimental condition uses a lactation consultant-peer counselor team to influence pregnant adolescents' beliefs and intentions about breastfeeding their newborns. The attention control (placebo) condition mimics the experimental condition, using an advanced practice nurse and peer counselor intervention team, and focuses on healthy pregnancy behaviors and labor/birth preparation. Teens in the two intervention groups attend two prenatal classes specific to their focus between the fourth and ninth month of pregnancy and receive telephone calls from a peer counselor. Teens in a usual care group receive no interventions beyond their standard prenatal care and education. After giving birth and still in the hospital, teens in the intervention groups receive a peer counselor phone call and visit. Breastfeeding teens in the experimental group also receive a breastfeeding counselor visit. After hospital discharge, breastfeeding teens from both intervention groups continue to receive peer counselor telephone support and, in the experimental condition, breastfeeding counselor phone calls for four weeks. Breastfeeding teens from all three groups complete short telephone interviews until six months after birth or until they stop breastfeeding.