Transrectal ultrasound allows tissue characterization of normal and abnormal internal anatomy of the prostate and therefore provides valuable information for the study of prostate cancer. In an early-detection program setting, the hypoechoic lesion proved to be twice as sensitive as a palpable abnormality in predicting the presence of cancer; for every two cancers detected by transrectal ultrasound, one was detected by digital rectal examination. When the presence of a hypoechoic lesion was the criterion for biopsy in a clinical setting, 41 percent proved to be cancer. Sixty-eight percent of these cancers were palpable; thus, for every four cancers detected by transrectal ultrasound, three were detected by digital rectal examination. Hence, in our diagnostic settings, transrectal ultrasound is more sensitive than digital rectal examination. Because transrectal ultrasound can measure tumor size and offer information regarding tumor spread, we recommend that transrectal ultrasound-guided biopsy be performed first on all palpable lesions. Up to 50 percent of negative biopsies guided by palpation have subsequently proved to be cancer with transrectal ultrasound-guided biopsy. If transrectal ultrasound-guided biopsy of a palpable lesion does not reveal cancer, however, a biopsy guided by palpation should be performed. Strategic transrectal ultrasound-guided biopsy for staging should be performed to obtain tissue from areas where microscopic extracapsular tumor extension is likely to be present. Based on presently available evidence, broader implementation and evaluation of transrectal ultrasound, a tool to be complemented by digital rectal examination and prostate-specific antigen, is advocated for the early detection of prostate cancer. It is hoped that the use of transrectal ultrasound will lead to increased survival, with good quality of life, in a cost-effective manner, for men at increasing risk from prostate cancer in the aging national population.