The aim of the exercise was to improve body health including the immune system function. However, several studies have observed the suppression of immune response in athletes who were trained with strenuous exercise. Recruits who have been in the recruitment-training program for 8 weeks might also have immune suppression. Twenty males, aged from 21 to 23 years in Chulachomklao Royal Military Academy infantry battalion volunteered to participate in this study. They were asked to wear a Polar Accurex Plus Telemetric heart rate monitor during the training period. Tuberculin skin test which is the screening method for cellular immune responses was significantly decreased at post-training compared to the pre-training (p<0.02). The levels of serum IgG and IgM at pre-training, 4th week, 8th week and one week post-training were significantly decreased at the initiation period, which were compared with pre-training and 4th week of training (p<0.01), and returned to normal at the 8th week of training and one week post-training. The level of circulating immune cells and number of CD markers (CD3, CD4, CD8, and CD56) were not significantly changed throughout the training period. This study demonstrated that subjects who underwent the recruit-training program were able to improve their health after the period of training i.e., in the adaptation period. The decrease in the initiation period could be compensated with proper diet and enough rest.