The introduction of solids and formula was studied among 506 breastfed infants in Uppsala, Sweden, based on daily recordings during the first year. The mothers had previously breastfed at least 1 infant for at least 4 mo. Thirty-four per cent of the infants were introduced to solids before the age of 4 mo (4-6 mo is recommended in Sweden). Accustoming the infants to solids was a lengthy process. Life-table analyses showed a median duration of 28 d from the first introduction of solids to consumption of >10 ml daily, and 46 d before the infants ate > or = 100 ml of solids in 1 d for the first time. These durations were longer the younger the infant was at the introduction of solids. Thirty-two per cent of infants given formula consumed > or = 100 ml the first time it was given, and 49% did so within I wk, regardless of infant age. CONCLUSION: Parents and healthcare personnel need to be aware that accustoming breastfed infants to solid food is a lengthy process, and that there is a strong age effect on this duration. It is also important to consider what consequences the (usually) more abrupt introduction of formula might have on breastfeeding.