Sonographically guided biopsy is a relatively new means of diagnosing prostatic cancer. The safety and efficacy of this modality in detecting cancer were assessed in a prospective study in which symptomatic patients (20) or those with palpable prostatic abnormalites (53) underwent prostatic sonography with sonographically guided biopsy when indicated. All patients with either a negative sonogram or a negative sonographically guided biopsy underwent subsequent evaluation by digitally directed prostate biopsy, transurethral prostatic resection (TURP), or both. The data from this study suggest that sonographically guided biopsy detects a high proporton (89%) of palpable prostate cancers (when compared with subsequent digitally directed biopsy) and “all” nonpalpable cancers (when compared with subsequent random core biopsy of the prostate and TURP). Only 3 of 47 (6%) patients who underwent sonographically guided biopsy had a complication from the procedure; all problems were minor. On the basis of these data, it appears that sonographically guided biopsy is a safe and effective means of diagnosing both palpable and nonpalpable prostatic cancers.