The impact of an unanticipated primary cesarean section on the mother, on the infant, and on their interaction was studied during the perinatal period and at 1 month following delivery. Thirty-four mother-infant pairs participated in the study. Fourteen subjects delivered by nonelective, nonemergency cesarean section. Twenty mothers, who delivered vaginally, served as the controls. All subjects had attended a series of prepared childbirth classes. Maternal questionnaire and infant observational data were collected on day 2 and on day 30. Mother-infant interactions in teaching and play sessions were assessed on day 30. The cesarean group was found to have a higher number of obstetrical complications, an increased incidence of maternal depression, and a more difficult convalescence. Previous experience with children emerged as an important mediating variable in the analysis of maternal affective status. No infant behavioral differences were detected as a function of mode of delivery. The discussion highlights the interventions that can be utilized to minimize the negative emotional consequences for women who deliver by cesarean section.