The Motor Inhibition Test, which measures "impulse control," requires the child to perform three motor acts. These acts are: walking a distance of six feet on a five-ince wide runway; drawing a line, using ruler and pencil, between two points 8-1/2 inches apart; and winding a toy jeep up to the rear of a toy two truck, a distance of 30 inches, so that it can be taken to the repair shop. The "truck" subtest proved unsatisfactory in Year 1 and was eliminated from subsequent tests. Its scores were not included in analyses of the interrelations of measures in Year 1. The walking and drawing subtests were combined into an average time score for each subject, and these data were examined by analysis of variance (age x sex x SES), using only those subjects tested in both Years 1 and 2. Age analyses for both years favored the older subjects, although the differences were very small in absolute magnitude. SES, i.e., mother's education, had a highly significant effect across years, with scores increasing as mother's education increased. Motor inhibition ability correlated significantly with other measures of competence and achievement in the longitudinal study battery. A general "impulsivity" dimension did not emerge. Tables provide means, standard deviation, and percentile distributions. (For related documents, see TM 003 174-186, 188-198.) (DB)