Transrectal ultrasonography is a relatively new diagnostic technique that has received much of the same enthusiasm that often is associated with the introduction of other new diagnostic or therapeutic instruments. The study allows for imaging of the prostate but benign conditions often cannot be differentiated reliably from malignant ones. The technique has clinical application in staging, monitoring tumor response to therapy and assisting in biopsy. Its role as a screening study when used either alone or in combination with other diagnostic tests has yet to be determined and well controlled, carefully performed investigations with state of the art instruments probably will help to establish the role of this examination when used for this purpose.