The decision to breast feed is important both for the mother and infant. Many federal programs are encouraging breast feeding in our society. However, there have been little data to study the demographic and social factors affecting the mother's decision. 100 new mothers were selected in the hospital and verbally responded to a 3 page questionnaire within the first few days postpartum. The interview consisted of an open-ended section aimed at eliciting a wide variety of influences, a series of demographic questions which focused on the marital, economic, and ethnic status of the mothers, and a sequence of attitude questions about infant nutrition. 84 mothers selected to breast feed (BF) while 16 mothers chose a commercial formula (CF). There were no differences between the groups in race, number of children, duration of breast feeding previous children, or the family main provider. 69% of the BF mothers cited the baby's health as the main reason for their choice. The CF mothers attributed maternal factors rather than infant factors as the main reasons for their choice. These mothers felt time constraints (18%), inexperience (18%), and the mother's work/school (19%) as major factors to use CF. Both groups reported that their doctors did not recommend BF (77% BF and 69% CF). However, more than half of each group claimed to be most influenced by the opinions of their doctors. Mothers who had chosen to BF were older(23-36 vs. 18-22 yrs old), more likely to be married, have a higher yearly income (>$15,000), more educated (high school graduate and beyond), and less likely to receive federal assistance than the CF mothers. There was a disagreement between the two groups concerning which type of feeding was easier. The BF mothers felt that nursing is easier, while most of the CF mothers felt that formula feeding is easier (P<0.03). In summary, there are major social and demographic factors influencing mother's decision to breast feed or not. We speculated that programs to increase breast feeding must consider these factors.