OBJECTIVES: This study examined the effectiveness of a hospital program to promote exclusive breast-feeding in Santos, Brazil. METHODS: In a prospective design, women who delivered at a hospital with an active breast-feeding promotion program (n = 236) were compared with women who delivered at a nearby control hospital (n = 206). RESULTS: The two groups had similar demographic characteristics and previous breast-feeding histories. Exposure to breast-feeding activities, assessed by maternal recall prior to discharge, was universally high at the program hospital and universally low at the control hospital. Multivariate survival analysis showed that exclusive breast-feeding lasted 53 days longer among women who delivered at the program hospital. CONCLUSIONS: Hospital-based breast-feeding promotion programs may be effective in extending the duration of exclusive breast-feeding.