Of 309 patients with verified breast carcinomas, preoperative mammograms were positive for 66%. This detection rate probably would have been higher if mammograms had not been omitted for many clinically obvious breast carcinomas during the seven-year period of study. The significant occurrence of false-negative examination results when mammography is used under day-to-day clinical conditions emphasizes the prime importance of physical examination in the recognition of breast carcinoma. The procedure is of greater than supportive diagnostic value, however, in the detection of breast carcinoma, because a significant number (11% in this study) can be detected early only, or primarily, by mammography. Categorizing patients into "high-risk" or "problem" cases provides selection for the vital and practical use of mammography in periodic screening and supports decisions in clinical management.