Abstract: Background and Objective: Despite the tremendous health benefits exercise training confers on the cardiac functions or coronary heart disease, the precise mechanisms by which exercise training improves heart function and cardiovascular disease are not well investigated. This study was designed to investigate the association between leukocyte count and maximal oxygen uptake in trained and untrained healthy adult males. Materials and Methods: Data were collected from 20 trained and 20 untrained adult healthy males of age (18-25 years), weight (60.25±1.3 kg) and height (1.76±0.0 m). The evaluation was completed between November 1, 2013 and January 31, 2014 in the Department of Human Physiology, of Ahmadu Bello University Zaria, Nigeria. The study procedure was approved by the Ahmadu Bello University Teaching Hospital Human Research Ethics Committee. A non-exercise regression equation was performed to determine the estimated maximal oxygen uptake (VO2 max). Statistical analysis was done by using student’s unpaired t-test with the social sciences (SPSS) software (version 20.0 for Windows; SPSS Inc., Chicago, IL) was used. Linear regression analysis was also used for prediction of any association. The level of significance was set at p<0.05. Results: The univariate regression analysis showed that VO2 max was correlated with leukocyte counts. VO2 max was negatively and positively associated with leukocyte counts in the trained (r = -0.218, p<0.05) and the untrained (r = 0.030, p<0.05) respectively. Conclusion: These results suggested that VO2 max is a sensitive factor of inflammatory status that confers cardiovascular protective effects in the trained adult males.