Two mental tests were given to physically “fit” ( N = 13) and “less fit” ( N = 9) male students. Test 1 consisted of the 30 odd-numbered matrices from the Standard Progressive Matrices (1960) and test 2 of the 30 even-numbered ones. Throughout test 1 Ss performed a physiologically “moderate” work level on a treadmill and throughout test 2 a physiologically “unduly heavy” work level. The cardiovascular responses indicated a significantly higher exertion level in the “less fit” group during test 2. Between group differences on test scores and time taken for test completion were insignificant on test 1 but significant on test 2, the “fit” Ss scoring higher and taking longer time. Within-group comparisons indicated that the “fit” Ss scored the same on both mental tests but took longer time for test 2, whereas the “less fit” scored significantly lower on test 2, taking shorter time for its completion.