Five hundred college 5s of Caucasian ancestry (256 men, 244 women) were trained on the United States Air Force Rotary Pursuit apparatus for one hundred 20-sec. trials spaced by 10-sec. rests. Results obtained were the following: (a) Mathematical forms of the percentage time-on-target curves were independent of aptitude; (b) curves at five ability levels were exponential and highly predictable (average error < 0.3%); (e) significant trend differences revealed early divergence and later convergence; (d) initial ability, acquisition rate, and final level were positively correlated; (e) no significant age differences were found within the range of 17-41 yr.; (/) men were superior to women in tracking skill (more accurate, less variable), maintaining an average lead of about 7.8% time on target; (g) interactions with practice were found between aptitude and sex; (h) intratrial