The U.S. cancer mortality per 100,000 for both sexes rose, from 1950 to 1967, for blacks from 147 to 177, an increase of 20%, while it remained unchanged for whites at 150. The female cancer mortality rate declined for blacks from 146 to 142, a decrease of only 3%, while it declined for whites from 139 to 126, a decrease of 9%. The male cancer mortality rate rose for blacks from 147 to 220, an increase of 50%, while it increased for whites from 158 to 181, an increase of only 16%. In 1950, the cancer mortality rate for both sexes was 2% lower for blacks than for whites, but, by 1967, it had become 18% higher. Of the 58 most frequent U.S. sex-specified cancer types, 29 increased slower in whites, 9 decreased faster in whites, 14 showed no significant differences, and only 4 (malignant melanoma and reticulum cell sarcoma in both sexes) increased faster in whites. Environmental factors are the most likely causes for this alarming rise of cancer in U.S. blacks.