Ten healthy, sedentary males, ages 23 to 56, participated in a 6- week supervised strengthening program in which five subjects exercised and five did not. Peak torque (PT) and total work (TW), and the percentage and absolute numbers of CD4 T cells, CD8 T cells, and NK cells were measured before, during, and after exercise. PT and TW showed significant increases over time only when the two groups were combined. There were no significant changes in the percentages and absolute numbers of CD4 T cells, CD8 T cells, and NK cells. Pearson correlations between PT and TW were significant: t=.97, p=.001. NK cell distribution was negatively correlated with CD8 T cells: r=.56, P=.009. CD4 cell distribution was weakly correlated with PT (r=.45, P=.047) and with TW (r=.56, P=.01). The correlations between CD4 and PT, and CD4 and TW imply that there is a modest association between these measures and CD4 cell distribution. The study was completed in January 1996.