Some baseball pichers have the symptom-complex of the elbow joint due to repetitive throwing. The Hyperextension overload syndrome is symptom-complex caused by impingement between olecranon tip and fossa during hyperextension of the elbow. The patients of hyperextension overload syndrome is have some pathology of his elbow such as bony spur on olecranon tip, intra-articular loose body or degenerative arthritis. And they complaint of pain or limitation of extension. The authors diagnosed and treated five cases of hyperextension overload syndrome. All of them had flexion contracture. Three cases of them had cubitus valgus. But no had medial instability of the elbow. Three cases of them had tenderness on the olecranon tip. Four patients treated by excision of osteophyte or loose body with arthroscopic or open operative technique.