Eight cases of primary malignant giant cell tumor of bone were reviewed. There was a wide range in age from 17 to 76 years, with the sixth decade of life being the most common. The tumor was more frequent among females (male to female ratio--3:5). The most common sites of occurrence were in the region of the knee, with the distal end of femur and the proximal end of tibia affected in three and two cases, respectively. Pain and swelling of the involved regions were the most common complaints. The roentgenographic and pathologic features and the treatment were analyzed in detail. Although these cases were considered malignant, the follow-up periods varying from 4 to 15 years were available in six of the eight cases; only one patient died of tumor, 8 months after the surgical procedure. One patient died of unrelated cause, but the others were all alive with no evidence of disease. The pertinent literature was analyzed and examples of secondary malignant giant cell tumors of bone were compared to those of this present series to delineate differences in natural history and clinicopathologic features. It was clearly established that primary malignant giant cell tumor of bone is a separate entity with a more favorable clinical behavior, particularly if the disease process is eradicated early on either by cryosurgery, en bloc radical resection, or amputation.