We prospectively studied 500 infants born consecutively in a university-affiliated community hospital in Copenhagen, Denmark, over the first 12 months of life using a detailed monthly mailed questionnaire (overall response rate = 73%) which focused on feeding practices and illnesses. Seventy-seven percent of respondents breast-fed their infants at 1 month of life compared to 19% at 12 months of life. Analysis of breast-feeding behavior using survival analysis showed that 50% of the mothers who breast-fed since the first month of their infant's life were still breast-feeding at 7 months of life. Also, there was a greater than two-fold increase in the rate of discontinuation of breast-feeding for infants in daycare compared to infants not attending daycare (RR = 2.08, 95% CI = 1.43, 3.01). Discontinuation of breast-feeding was not significantly associated with the number of children in the family or with social class. These results give insight into infant feeding patterns in a developed country and suggest that: (1) breast-feeding is the dominant method of feeding during the infant's first year of life, and (2) the rate of discontinuation of breast-feeding is increased by the entry of these infants into daycare.