We report one case of osteoid osteoma of olecranon fossa in a female with pain and functional limitation of the elbow. The articular variety of osteoid osteoma is relatively uncommon and its diagnosis is very difficult. Conventional radiology, tomography and scintigraphy are employed for diagnosis, however computed axial tomography is particularly useful for diagnosis and correct treatment of osteoid osteoma of olecranon fossa.