In order to determine the proportion of infants seen in safety-net health clinics whose mothers initiated and sustained breastfeeding and to assess predictors of breastfeeding in this largely minority patient population, charts were reviewed for infants treated in the eight Philadelphia Health Centers. Breastfeeding was initiated by 42%; 7.5% breastfed for 180 or more days. Race/ethnicity, mother's age, birth weight, and prematurity were not associated with breastfeeding initiation or maintenance. There were differences in initiation rates between patients born in different hospitals, and between patients seen in different health centers. Hospital and health center differences in breastfeeding initiation and health center differences in breastfeeding maintenance may reflect practice variations and unmeasured differences in patient populations. While breastfeeding rates in this population remain far below targets, the substantial proportion of mothers who did breastfeed and large variations between facilities demonstrate that breastfeeding is possible and can be successfully promoted among economically disadvantaged mothers.