Of 21,855 consecutive women prospectively studied with mammography, physical examination, and high-resolution ultrasonography when appropriate, 558 received a diagnosis of nonpalpable, probably benign lesions. Follow-up mammography was recommended for these patients. Characteristically benign lesions and palpable masses were excluded from analysis. The positive predictive value for detection of a nonpalpable, probably benign breast lesion was 0.017. Nine patients ultimately proved to have carcinoma; two of them had noninvasive carcinoma, and two had axillary node metastases. The positive predictive value for detection of a nonpalpable, probably malignant lesion was 0.47. The policy of recommending mammographic surveillance for nonpalpable, probably benign lesions, a viable option for radiologists, has the capability of lowering the rate and therefore the costs of biopsy procedures with negative results.