The purpose of this study was to investigate the effect of 12weeks of aerobic training with different exercise intensity on blood lymphocyte number. Healthy college-aged males(22.53±1.91yr) were participated in the maximal exercise test before(N=32) and after(N=30) 12weeks of aerobic training. The subjects were divided into two groups; control groups(N=8), training group(N=24). Then training group was divided into three subgroups; 50%HRR(low, N=8), 70%HRR(middle, N=8), 85%HRR(high, N=8). Two persons were eliminated during the training. To investigate the effect of aerobic training on blood lymphocyte number were measured at rest, immediately after exercise and 60min recovery. Maximal exercise testing was used the Bruce protocol on the treadmill. VO_(2max) were measured by maximal exercise testing, exercise intensity was determined for aerobic training treatment a basis of this measured values. speed and grade at 50%, 70%, 85%VO_(2max) and 50%, 70%, 85% of %HRR gained pre test were produced and applied. The programs of exercise groups were aerobic treadmill exercise for 12weeks. Three groups performed almost 40min, 30min, 20min per day(3days/week) by 300㎉ respectively. Venous blood were drawn at the forearm antecubital vein at rest, immediately after exercise and 60min recovery. First, there was no significant differences of T-cell among four groups in number, but there was significant differences before and after training and sampling time in number(P＜.01, .001). Second, there was no significant differences of B-cell among four groups in number, but there was significant differences before and after training and sampling time in and number(P＜.01, .001). Also, there was no interaction effects. Third, there was no significant differences of NK-cell among four groups in number, but there was only significant differences before and after training in number(P＜.01). there was significant differences of sampling time in number(P＜.001). There was no interaction effects before and after training and sampling time in number. Forth, there was no significant differences of Th(CD4+)/Ts(CD8+) ratio among four groups, but there was significant differences before and after training and sampling time(P＜.01, .001). Also, there was significant differences interaction effects among groups, before and after training, and sampling time(P＜.05). Results indicate that the exercise-induced lymphocyte subset reduction is transient and suggest that it is not dependent upon training intensity in the case of college-aged male, but aerobic training of various intensity is associated with sustained alterations in immune function, both at rest and when exercising.