The present paper has described a large-scale factor analysis study of performance in the relatively unexplored aptitude area of psychomotor skill. A large number of apparatus and printed psychomotor tests was selected or specifically designed to measure certain ability categories hypothesized to exist from the results of previous research in this area. After extensive pretesting, the tests were assembled into a battery and administered to 400 Ss. The correlations among scores on these tests were then subjected to a Thurstone centroid factor analysis. The results of the study appear to confirm the existence of the following relatively independent factors in psychomotor skill (1) Wrist-finger speed; (2) Finger dexterity; (3) Rate of arm movement; (4) Manual dexterity; (5) Arm-Hand steadiness; (6) Reaction time; (7) Aiming (eye-hand coordination); (8) Psychomotor coordinations; (9) Postural discrimination; and (10) Spatial relations. Two additional factors were isolated but their interpretation or significance remains doubtful. The results were discussed with respect to the factor composition of individual tests, the utility of certain printed tests designed to reproduce apparatus test variances, and the contribution of these factors to certain kinds of more complex psychomotor performance.