Carcinoma of the prostate can be diagnosed definitively only by biopsy. Needle aspiration biopsy obtained with a flexible 20- or 22-gauge needle may provide this diagnosis. This method has been utilized widely in Scandinavia but rarely in the United States. Fifty-one patients were so biopsied with concomitant punch biopsy. Of the 32 cases of carcinoma, there were abnormal cells in 27. There was no false-positive diagnosis. Although complications that occur with routine punch biopsy may be significant, there was no secondary to aspiration biopsy. The procedure should be used as a primary tool in the diagnosis of prostatic carcinoma.