Trans-rectal ultrasound (TRUS) guided needle biopsy for diagnosis or exclusion of prostate cancer. An ultrasound image from the rectal probe is used to locate areas of the prostate to be biopsied. The hand-held biopsy gun has a fine needle which is inserted through the rectal wall and into the prostate. Upon activation, a sliding sheath extracts a thin cylinder of tissue (core). Cores from different regions of the prostate will be extracted and examined to determine the extent of any cancer.