Reliable data on the impact of physical training on light infantry units in terms of injuries and time loss are sparse. This study evaluated a light infantry unit (n = 181) prospectively and followed it throughout one year of infantry training and operations. Fifty-five percent of the soldiers (n = 101) experienced one or more injuries. Eighty-eight percent of the injuries were training-related conditions, which resulted in 1,103 days of limited duty. Lower extremity overuse injuries were the most common type of injury documented. Fractures accounted for the greatest number of days of limited duty. Risk factors for training-related injuries identified by this study were cigarette smoking, high percentage of body fat, extremely high or low body mass index, low endurance levels, and low muscular endurance levels (sit-ups). Logistic regression showed that cigarette smoking and low endurance levels were independent risk factors for training injuries. These data indicate that the incidence of training-related injuries in infantry units is high. A number of modifiable injury risk factors were identified, suggesting that many of these injuries may be preventable.