The transeference of two antibiotics, i.e. cefmetazole (CMZ) and fosfomycin (FOM), into prostatic tissues was examined. Prostatic tissue samples were obtained from patients with benign prostatic hyperplasia while undergoing open prostatectomy or transurethral resection of the prostate (TUR-P). 2 g of CMZ or 4 g of FOM was intravenously administered within about 10 minutes starting 1 hour before the removal or resection of the prostate, and blood samples were collected at the end of the administration and during surgery. In TUR-P, resected prostatic tissues were washed with the TUR perfusate and the antibiotic in the tissue was presumed to be released into the perfusate. The following preliminary experiments were, therefore, carried out. The removed prostate was divided into three segments, i.e. urethral region, central region and capsular region, and the CMZ or FOM level in each tissue was measured. The remaining tissues were cut into small pieces for immersion in the TUR perfusate for 10-90 minutes. The tissue fragments were removed every 10 minutes to measure the tissue concentration of CMZ or FOM. The concentration of CMZ or FOM in the prostatic tissues did not vary among the three regions, however it markedly decreased with increase in the period of immersion. This suggested that the concentration of these agents into the prostatic tissues was represented by the concentration in the tissues near the urethra obtained immediately after the start of TUR-P.(ABSTRACT TRUNCATED AT 250 WORDS)