Temperament of 4-month-old infants of diabetic (n=l6) and nondiabetic (n=l8) mothers did not differ reliably in terms of maternal ratings on the Infant Behavior Questionnaire (IBQ) (Rothbart, 1981). Item analysis indicated that scales on a reduced version of the IBQ maintained high internal reliability. Discrete behaviors, adapted from the Infant Behavior Record (Bayley, 1969), and conceptually related to each scale of the IBQ, were observed by mothers and by a trained observer during the infants' well-child examinations. Group differences for activity level and duration of orienting were obtained by the trained observer. These differences were similar in pattern to those found by Yogman, Cole, Als, & Lester (1982) on newborn infants of diabetic mothers. Mothers' observations were reliably correlated with those of the trained observer on the following scales: (a) smiling and laughter, (b) fear, (c) distress to limitations, (d) soothability, and (e) duration of orienting. Mothers' observations were not reliably correlated with those of the observer on (f) activity level. The behavioral items were not significantly correlated with their respective scale on the IBQ. With subjects from both groups combined, neither gestational age nor ponderal index was related to temperament ratings or to discrete behaviors. Results failed to support the hypothesis that diabetic-related biobehavioral vulnerabilities and psychoendocrine mechanisms mediated temperament in 4-month-old infants. However, differences in discrete behaviors were present. Further studies are needed to determine whether differences of discrete behaviors affect later development. / M.S.