Breast feeding is customary in Senegal and most of Africa, but as in other potential markets, multinational companies have attempted to introduce infant formula for bottle feeding. 100 mothers each were interviewed in Dakar, Pikine, Saint Louis, Kaolack, and Ziguinchor between December 1981 and May 1983 to assess the spread of bottle feeding. Mothers were classified in good, average, or poor income and educational groups. Women not breast feeding exclusively were asked their reasons why not. 368 of the mothers (73.6%) breast fed exclusively, 117 (23.4%) mixed breast and bottle feeding, and 15 (3%) bottle fed exclusively. The duration of breast feeding ranged from 6-24 months and averaged 14 months. In Saint Louis, Kaolack, and Ziguinchor between 80-84% of mothers breast fed exclusively, but in Pikine 39% and in Dakar 34% of mothers mixed breast and bottle feeding. Their reasons for doing so included employment of the mother, urbanization, and the impact of advertising. The trend to exclusive bottle feeding is still weak in cities and towns of Senegal, ranging from 1-5%. Breast feeding was the predominant mode at all socioeconomic levels except in Dakar, where wealthier women tended to employ mixed feeding. In Ziguinchor, Saint Louis, and Kaolack, breast feeding predominated at all educational levels. More educated women in Dakar and Pikine tended to mix breast and bottle feeding, but women with average educational levels breast fed. Women who bottle fed did so exclusively for professional or medical reasons.