Abstract  Although bone stress injuries are common in male military trainees, it is not known how common they are in female trainees. It also is unclear whether asymptomatic bone stress injuries heal if intensive training is continued. We prospectively followed 10 female trainees of a military Reserve Officer Course. The subjects underwent clinical and MRI examinations of the pelvis, thighs, and lower legs at the beginning, once during, and at the end of their 3-month course. We identified two to five injuries in every female trainee, all of whom already had the injuries at the beginning of the officer course. None of these injuries increased their severity despite vigorous training. Two-thirds were asymptomatic and low grade. Femoral and tibial shafts were the most common locations. Higher-grade injuries were more likely symptomatic, but regardless of the MRI findings, female trainees expressed only mild to moderate symptoms. Asymptomatic, low-grade bone stress injuries of the femoral and tibial shaft are common in female recruits undergoing heavy physical training. Because these injuries seem to remain constant or even disappear despite continued heavy physical activity, we do not recommend routine screening of asymptomatic trainees. As some bone stress fractures may have severe consequences (eg, in the femoral neck), symptomatic bone stress injuries should be examined and treated.