Breast- and formula-fed infants were compared with regard to behavior patterns, especially crying behavior. A diary concerning seven behaviors was completed by 188 mothers of breast- and formula-fed infants at the well baby clinic. Breast-fed infants were fed more frequently with longer feeding duration. They slept more, but their long bouts were shorter than those of formula-fed infants. The crying pattern of formula-fed infants was different from that of breast-fed infants in that they displayed an evening cluster and a 7-week peak of crying. Since the educational level of the formula group mothers was higher and there are more later born babies in that group, it is speculated that these mothers have a Westernized tendency in their caretaking style and, as a result, the crying pattern of formula-fed infants are similar to that of Western babies. In multivariate analysis, contact, play, sleep durations and mothers' education contributed significantly to cry duration. These results imply that contact with the mother and other caretaking practices are closely associated with infants' crying.