In a private pediatric practice, 94 infants who were breast-feeding were followed for the first 2 months of life in order to define the frequency of cessation of breast-feeding and to identify factors that would predict mothers and infants at risk for early cessation. At 8 weeks, 30% of the mothers had stopped nursing. Factors associated with cessation were: maternal lack of confidence in breast-feeding (P less than .001); anticipated duration of nursing less than 6 months (P = .002); ratings by the nursery staff of infant's excessive crying (P = .007), infant's demanding personality (P = .007), trouble with feeding (P = .001), and future trouble with feeding (P = .004). Together, these factors predicted 77% of the mothers who terminated breast-feeding. Supplementing with formula before the 2-week office visit also led to termination of breast-feeding by 8 weeks (P = .006). This decision was frequently made without medical advice. Nearly 64% (14/22) of the mothers who added formula within the first 2 weeks did so without contacting the pediatric practice.