167 patients with a mean age of 64 years underwent digital rectal examination (DRE), transrectal ultrasonography with a 7-MHz transverse and/or longitudinal transducer, followed by prostatic biopsy under ultrasound guidance. 231 biopsies were performed. 74 peripheral hypoechogenic zones were demonstrated. The sensitivity of DRE was 82% and the specificity 91%. The sensitivity and the specificity of ultrasound were respectively 69 and 83%. On 123 patients with normal DRE, 19 hypoechoic zones were detected and 2 patients had a positive biopsy (11%). On 104 patients without hypoechoic zone, 5 biopsies were positive (5%). The use of transrectal ultrasound scanning is able to multiply the number of impalpable cancer by 2, but in only 3 lobes, a hypoechogenic zone associated with a normal rectal examination was confirmed to be a cancer on biopsy. These cases represent 5.5 of the 56 positive biopsies, 4% of the hypoechogenic zones and 1.6% of the investigated patients with normal rectal examination. No impalpable cancer of 5 mm or less was detected by high resolution ultrasonography. DRE is still the most reliable examination for the diagnosis of prostatic cancer. Ultrasonography is a useful complement, particularly by allowing collection of tissue interpretable by the histologist in 100% of cases.