Roentgenographic changes consistent with osteochondrosis of the proximal humeral epiphysis were observed in five young baseball pitchers complaining of shoulder pain in the throwing arm. The symptoms and findings were quite similar to the previously reported involvement of the medial epicondylar epiphysis or "Little Leaguer's elbow."The act of throwing a baseball hard is an abnormal whip-like action which places a forceful repetitious traction strain on the shoulder joint. Shoulder pain in youngsters engaged in organized competitive swimming programs can also be explained in this way. Since these entities became evident with the establishment of organized baseball programs for boys in this age group, better medical supervision and rule changes to limit the amount of pitching until the epiphyses close, are urgently needed.