Patients with neuromuscular diseases have low levels of cardiovascular fitness and they fatigue rapidly during daily activities. The purpose of this investigation was to determine whether patients with slowly-progressive or non-progressive neuromuscular diseases could complete a 12-wk training program without untoward responses, and develop cardiovascular training adaptations. All eight patients completed the training program with better than 90% compliance. Resting creatine kinase and myoglobin in the group as a whole showed no change with training, though two patients did have definite elevations after training. Their VO2max increased by 25 +/- 5% with training and their relative increase in VO2max was not different from that of healthy subjects undergoing the same training. Heart rate reductions during submaximal exercise were somewhat delayed or non-existent in the two patients with Charcot-Marie-Tooth disease, a hereditary neuropathy. However, the six patients with myopathies had heart rate adaptations similar to those in healthy subjects. Thus, some patients with slowly-progressive or non-progressive neuromuscular diseases can undergo exercise training and in many cases demonstrate adaptations not different from those in healthy subjects. Patients with different diseases, however, need not respond uniformly, in terms of training adaptations or markers of muscle damage. Therefore, each disease must be considered individually.