Temperament stability over successive ages in the first 2 years of life was evaluated for 109 full-term and 81 preterm infants who were assessed at 6, 9, 12, 18, and 24 months. At each age, the infant was engaged in a series of age-appropriate vignettes in the laboratory, using a structured sequence of activities. Ratings were made of emotional tone, attentiveness, activity, and orientation to staff. Correlations indicated that, for full-term infants, there was significant stability across ages (6 to 9 months, 9 to 12 months, 12 to 18 months, and 18 to 24 months) for all variables. For preterm infants, stability across ages generally was not observed until later infancy, or was sporadic. The findings indicated that, for full-term infants, stable aspects of temperament were apparent during the first year of life. In contrast, individual differences were not as clearly defined for preterm infants until later ages.J Dev Behav Pediatr 9:6–11, 1988.Index terms:temperament, preterm, infancy, longitudinal, risk.