For a sample of 89 infant twins, multimethod assessments of temperament were obtained at 18 and 24 months of age. A standardized laboratory sequence elicited behaviors that were videotaped and then rated on scales representing emotional tone, activity, attentiveness, social orientation to staff, and vocalizing. To these ratings were added ratings of the infants' reactions to the restraint required for physical measurements. At each age, the series of ratings were condensed to a single score representing each of the behaviors, and the condensed scores were subjected to factor analysis. A principal dimension emerged at both ages that combined positive emotional tone, sustained attentiveness, social approachfulness to the staff, and calmer acceptance of restraint. Category scores from the Toddler Temperament Scale, completed by the parents at each age, providing a strong first factor denoted by the following categories of temperament: mood, adaptability, approach, intensity, and activity. Correlations between the first factor scores extracted from the laboratory and questionnaire data provided significant evidence of convergent validity for the 2 independently determined dimensions of temperament of both ages. Coordination of these temperament dimensions with analogous dimensions obtained at 12 months further provided evidence of stability of temperament across 6-month intervals during the second year. The results demonstrated the utility of a multimethod approach for establishing the core dimensions of temperament among toddlers.