Evidence indicates that aerobic fitness is positively associated with certain aspects of cognitive function in later years. What is not clear is whether fitness level affects cognitive performance under both timed and untimed conditions. The purpose of this study was to compare the performance of high fit versus low fit older adults on a timed versus an untimed information processing task. The timed Digit Symbol Substitution Test(DSST) and the non-timed Digits Backward Scale (DBS), were administered to 74 healthy older adults, ages 50 to 84 (M = 68.8). Aerobic fitness was estimated by performance on a 12-minute walk test, with subjects classified into high-fit and low-fit groups. Subjects were also classified into two age groups, younger (< 68) and older (≥ 68), in order to compare the relative effects of age and fitness level on cognitive performance. Data were analyzed using a 2×2 ANOVA with significance level set at.05. Results indicated that the high fit older adults scored significantly better(p <.05) on the DSST than did the lower fit subjects (55.3± 8.9 vs. 49.9 ± 10.4). No significant fitness effects were found on the DBS, nor were there significant age effects on either the DSST or the DBS. It was suggested that higher fit older adults may score better than lower fit older adults on timed cognitive tasks because of the positive influence of aerobic fitness on oxygen delivery, chemical production, and increased neurotransmission speed within the central nervous system.