To understand why some lower socioeconomic status mothers delivering at a state university hospital breastfeed, while others do not, 26 attitude items were administered in a survey of 358 mothers. A factor analysis of these items yielded four interpretable factors: benefits to infant, social inconvenience, personal inconvenience, and physical inconvenience-medical benefits to child. These factors were significantly related to breastfeeding within each level of ethnicity and marital status. The results imply that emphasizing the benefits for the infant, and providing strategies for minimizing personal inconveniences, should promote breastfeeding in these populations.