SummaryData on breast‐feeding, weaning, and the practice of giving night‐meals, collected in the prospective longitudinal growth‐study presented earlier, have been analysed for their association with various social and family factors and personality variables in the mothers. The following statistically significant relationships were found: 1. Boys are breast‐fed longer than girls. 2. Mothers in the higher age‐group (26 and over) continue breast‐feeding longer than do younger mothers (under 26). 3. Mothers of the highest social class (Graffar I+ 11) continue breast‐feeding longer than do mothers in the intermediate (Graffar III) and the lowest (Graffar IV+ V) social classes. 4. Mothers with higher education continue breast‐feeding longer than do mothers with only elementary school education. 5. In the lowest social class, mothers who live in old‐fashioned houses stop breast‐feeding earlier than do mothers living in modern houses. 6. Some personality traits of the mother are more often than others associated with long‐continued breastfeeding.No statistical relationships were demonstrated between the duration of breast feeding and overcrowding or the child's successional number in the family.The reasons for weaning were analysed. “No or insufficient milk” was the most common reason given by mothers who weaned their babies before 6 months. Gainful employment was of very little importance as a reason for weaning.The mothers' attitudes towards breastfeeding in the child's first and third months of life were generally positive. The duration of breast‐feeding cannot be predicted from the attitude declared by the mothers.The frequency of night‐feeding on the return home from the maternity hospital was 85% and at 3 months 25%. The boys received night‐meals for a significantly longer period than did the girls. The mother's age, the child's successional number in the family, social class, the duration of breast‐feeding and the mother's attitude to breast‐feeding showed no association with the continuation of night‐feeding.