A group of clinically depressed mothers and their infants were studied to ascertain effects of mothers' emotional condition on children's behavior and development. Participants in the study were 29 families with an infant believed to be at psychiatric risk. Maternal depression was assessed at the time of family intake with the Center for Epidemiological Studies Depression scale; infants were assessed using both observational and psychometric measures at 7, 12, and 18 months of age. A closely matched control group was assessed at 12 and 18 months of age. Videotapes of 40 minutes of spontaneous mother-infant interaction were made in each family's home. A subsample of 13 mothers was asked to engage in a structured face-to-face interaction for 6 minutes after spontaneous interaction. Findings revealed that the behavior of most mothers was neutral to negative in affect expression. Depressed mothers' involvement with their child was primarily intrusive or angry. In contrast to that of the mothers, infant behavior was more consistently neutral to negative in affect expression. Small but significant differences between depressed and case-control infants were found in mental and motor development. It is concluded that infants' affective and cognitive development may be undermined by daily interactions with a primary caregiver behaving in a disengaged or intrusive way. (RH)