The purpose of this article is to report the effects of arm ergometry training on upper extremity strength, body composition, and oxygen uptake in a 13-year-old adolescent with myelodysplasia. The subject trained three times a week for eight weeks at 75% of maximum heart rate. The following measurements were determined before and after the training period: maximal and submaximal heart rate and oxygen uptake, percent body fat, and peak torque of the elbow and shoulder flexor and extensor muscles. The results indicated that maximal oxygen uptake and percent body fat did not change, but maximal physical work capacity increased from 274 kg . m/min to 569 kg X m/min. Heart rate and oxygen uptake decreased at each submaximal work load, and peak torque increased an average of 22.3% for the movements tested. We concluded that arm ergometry training in an adolescent with myelodysplasia can reduce the energy cost of performing submaximal arm ergometry work.