Repeated throwing of baseballs by juvenile pitchers is known to cause damages to bone and cartilage as well as soft tissue in the involved upper extremity. Authors present 4 cases of osteochondral lesion at capitellum of the humerus as a result of repeated insult by throwing baseballs in the juvenile pitchers. Pain and limitation of extension of the affected elbow were the commonest symptoms. Cystic change or osteochondral loose body was found on plain X-ray. Treatment consisted of rest and analgesic administration in the patient who has no loose body, while in case of having loose body it was removed surgically without further treatment to the crater. In spite of the rapid relief of the pain by these treatment, limitation of extension persisted for considerable period of time. It is strongly suggested not to overlook elbow pain in young adolescent whose bone is still growing and who can hardly withstand repeated insult to prevent the development of baseball elbow.