Norfloxacin (NFLX) a synthetic oral antibacterial agent of quinolone carboxylic acid, was given to 6 healthy men aged 23 to 29 years and weighing 57 to 88 kg (average 64.7 kg) at a dose of 200 mg (two 100 mg tablets) once after breakfast and its fecal and urinary recoveries were determined for 5 days after the administration. Fecal and urinary recoveries of NFLX or ciprofloxacin (CPFX) were examined under various experimental conditions where the drugs were added to the urine or feces. Effects of the drug on the clinical laboratory test parameters and side effects were also examined. The following results were obtained. 1. NFLX reached the highest level in the feces in 5 cases in 24 hours and in 1 case in 48 hours; average peak fecal level was 137.1 micrograms/g in 24 hours. Fecal recoveries were 2.32 to 36.90% in 5 days after dosing with an average of 13.83%. 2. Urinary levels of the drug reached their peaks within 24 hours (average 51.46 micrograms/ml) in all cases and then decreased. Urinary recoveries were 11.15 to 46.44% in 5 days after dosing. Both fecal and urinary levels of the drug varied greatly among the subjects. 3. The sum of the fecal and the urinary recoveries in each case varied from 13.47 to 76.88% (average 42.24%).(ABSTRACT TRUNCATED AT 250 WORDS)