Pigmented villonodular synovitis, bursitis and tenosynovitis may present a variable picture depended upon the site and whether they are localized or diffuse. In the localized form of the disease occurring in association with tendon sheaths, complete surgical excision should result in a cure. Local recurrences probably result from incomplete excision. The localized disease within the knee joint may represent a picture of internal derangement. Simple excision should result in complete cure. Diffuse pigmented villonodular synovitis (DPVS) poses a diganostic and therapeutic problem. Where possible, complete synovectomy is indicated but the recurrence rate after such surgery is unfortunately quite high. Radiation therapy should probably be considered only in patients in whom lesions recur after surgical synovectomy. Despite three decades of study, the etiology and pathogenesis of the lesion remains obscure. It is apparent, however, that the lesion is not a neoplasm and probably represents an inflammatory process.