Evidence suggests that cognitive ability declines with advancing age but that aerobic fitness can serve to minimize or even negate these declines. The purpose of this study was to examine the relationship between age, fitness, and retention. Twenty younger (M=24.2 years) and 18 older adults (M=66.6 years) practiced on the mirror star trace until they achieved a criterion. VO2max was measured. The number of trials required to reach criterion was predicted by VO2max, p < .001. and age, p < .02. Retention distance was also predicted by VO2max, p < .001, and age, p < .001. Analysis of relative alpha change at P3 and F4 indicated that a relative increase in left-hemisphere alpha and a relative decrease in right-hemisphere alpha were associated with retention errors. Thus, older and less aerobically fit adults required more trials to reach criterion and performed less well at retention, and changes in brain activity were associated with retention errors.