Enoxacin is a new quinolone derivative that is well absorbed after oral administration and shows good efficacy against the pathogenic bacteria usually isolated in urinary infections. We studied the diffusion of enoxacin in healthy renal tissue (13 patients) and adenomatous prostate tissue (16 patients) in surgical patients dosed with enoxacin preoperatively. The plasma and parenchymal concentrations were measured by high-performance liquid chromatography after 5 successive oral doses of 400 mg given at 12-hour intervals. The mean concentrations for the prostatic series were: 5.15 +/- 2.68 micrograms/g of adenomatous prostatic tissue and 2.07 +/- 1.38 mg/l of plasma 2 h after the last dose (r = 2.54); 2.5 +/- 1.7 micrograms/g and 0.98 +/- 0.8 mg/l, respectively, 15 h after the last dose (r = 2.61). The mean concentration of enoxacin in the kidney 3 h after the last dose was 13.93 micrograms/g (r = 7.35); the concentrations 12 h after the last dose ranged from 9.70 to 14.35 micrograms/g of tissue and from 1.1 to 2.3 mg/l of plasma (r = 7.76). Consequently, enoxacin appears to have interesting possibilities for the treatment of urological parenchymal infections.