Because of shrinking resources, the United States military will be forced to carry out its mission in the future with maximum efficiency. Medical problems reduce the efficiency of the training of soldiers. Our project documents the medical problems that occurred in infantry basic trainees and tests easily obtainable information for its ability to predict the impact of medical problems on each trainee. The study involved 649 trainees undergoing a 13-week cycle of basic and advanced infantry training in one of three companies at the United States Army Infantry Training Center, Fort Benning, Georgia. The most common reason for sick call attendance among this group of trainees was upper respiratory infection. While medical illnesses were frequently seen, they did not cause a great deal of lost training time. Training injuries such as foot and lower leg overuse syndromes and patellofemoral knee pain were the primary causes of time lost. The average trainee made 1.58 +/- 1.61 visits to sick call during the cycle, with a total of 4.53 +/- 8.49 days of training time limited by profile. However, many trainees made no sick call visits and the majority of trainees lost no time due to medical problems. The strongest predictors of medical impact on training were a history of cigarette smoking and the initial performance of the trainee on the three events of the Army Physical Fitness Test. Based on the results of this study, we recommend that the military consider cigarette smoking as a negative factor in the selection of recruits and consider that recruits be required to meet some standard of fitness prior to induction.