Of 96 [human] cancers which were detected as a result of the 1st annual screening of 10,470 volunteers, 46 were clinically occult. Forty-one of these were stage 1 or less carcinoma, and 26 of these 41 were minimal cancer. For the radiographic parameters used, the benefit of detecting these cancers vs. the risk of induced cancer is estimated as 103:1 and 65:1, respectively.