Condensing osteitis of the clavicle is a rare and benign idiopathic entity that is probably degenerative or mechanical in etiology. It is usually seen in women of late child-bearing age as a variably painful and tender swelling over the medial end of the clavicle. Radiographs show sclerosis and slight expansion of the medial one-third of the clavicle. Although malignant tumor of bone must be considered in the differential diagnosis of a disease that has such radiographic findings, numerous and expensive screening tests for a presumed primary malignant lesion are not recommended for most patients. It is recommended, however, that an excisional or (preferably) incisional biopsy be performed in all patients unless pain is insignificant and the clinical presentation strongly supports the diagnosis of condensing osteitis. Many patients who have slight pain do not need treatment. Anti-inflammatory medications are variably effective. Patients in whom the lesion is refractory respond well to excision of the medial one-third of the clavicle.