A short-term longitudinal study investigated the way parents come to perceive their infant's temperament as difficult, and to identify factors influencing parents' impression formation. Subjects were 40 middle and lower middle class breastfeeding mothers and their singleton newborns of 38 weeks gestation and 2500 grams birth weight. All mothers were ambulatory, responsible for "rooming-in" care, and had no histories of psychiatric or chronic physical illness. Multiple measures were employed to gather data during the infant's first week of life and again 7 weeks later. Findings from the newborn and second month periods are reported and future directions for research are pointed out. Concluding remarks assert that researchers should now begin to ask how and why parents derive their particular perceptions of their infants. (RH)