This study reports various aspects of the analyses carried out on the longitudinal data reported in a previous study (PS 007 345) for determining the general growth patterns and growth velocity of mental and motor development. Preliminary analyses focused on the selection of the growth curve, its evaluation in the 208 individual cases, and the subsequent decision that it did not present an accurate description of the data. To compensate, an approach was initiated which compared each subject to a common standard and classified the subject into one of three categories: fast, normal, and slow growth. Results indicated that subjects were equally divided among categories in mental growth and that one-half of the subjects were in the normal category in motor growth with the remainder equally divided between the other two. In measuring the growth velocity of mental and motor development a curve closely approximating the velocity pattern was fitted. Curve examination showed a prominent peak for both areas in the first six months followed by a gradual decrease in velocity that was less severe than that found in the observed data. Concluding discussion focused on the limitations of the growth curve and implications of the testing conditions. (SDH)