The clinical and pathological findings in 15 primary "pure" clear cell carcinoma of the ovary included in the Magee-Womens Hospital Tumor Registry from 1947 through 1974 are discussed. The ages of the patients ranged from 35 to 75 years (mean 53). The most common clinical finding was an abdominal mass in 14 cases. At surgery, five patients had extraovarian spread, one accompanied by ascitis. The tumors varied in diameter from 4 cm to 17 cm (mean 10.5 cm); grossly, about one-third were cystic, one-third solid and one-third had combined cystic and solid areas. Microscopically, four basic patterns were seen: papillary, tubular, solid, and cystic, and in several an admixture of the above. Clear cells predominated in 48% of the cases and 23% displayed hobnail cells. Most patients were treated by TAH & BSO or variants thereof, some followed by radiation or chemotherapy. Four patients died with cancer within 35 months after diagnosis; two others died of unrelated causes three and 12 years later. The actuarial survival was computed as 55% at five years. Five patients were stages as IIb (FIGO classification); four died with tumor and the remaining patient is alive with recurrent tumor in the pelvis 18 months after the original diagnosis. Three patients with tumors displaying the cystic pattern are still alive; two with a predominantly papillary pattern and vascular permeation are dead. It is suggested that survival rates in these 15 cases may be related more to the extent of the lesion at the initial presentation than to the gross or microscopic pattern.