To determine the efficacy of mammography in the detection of early breast carcinoma at an urban teaching hospital, the results of all breast biopsies performed between 1983 and 1987 that were preceded by mammographic examination were retrospectively reviewed. There were 503 women in this population. Malignancy was detected in 79 cases (15.7%); 21 were in situ and 58 were invasive. Among all nonpalpable malignancies, 53.0 per cent were in situ, while only 2.4 per cent of all palpable malignancies were in situ. An abnormality was found in 374 mammograms (74%), and 73 (19.5%) were malignant. The abnormality most likely to represent a malignancy (44% yield) was spiculated density, followed by clustered microcalcifications (25%), mass (22%), and asymmetric density (14%). Six malignancies were detected by biopsy for clinical indications, despite a negative mammogram (4.7% false- negative rate). The interpretation of mammograms by radiologists carried a 2.4 per cent false-negative rate. The mammographic features of mass, clustered microcalcifications, spiculations or asymmetric density should generally mandate breast biopsy, although the clinical examination should remain an important basis for management decisions. An aggressive approach toward screening mammography and breast biopsy based on mammographic criteria may enhance survival among women with breast carcinoma.