The elimination of enoxacin was investigated in 15 subjects, 10 of whom were hospital outpatients with renal disease and varying degrees of renal impairment. Each was given enoxacin orally (200 mg b.i.d.) for 7 days. Blood specimens collected over 24 hours after the final dose of enoxacin and urine collected during the 12-hour dose interval after the final dose were assayed for enoxacin by HPLC. The elimination half-life of enoxacin increased with worsening renal function. In general, patients with diminished renal function had lower plasma enoxacin clearance values than had normal subjects, and a statistically significant correlation between apparent oral clearance and creatinine clearance was observed. Excretion of enoxacin by the kidney accounted for 26% to 72% of the apparent plasma clearance in normal subjects. This was markedly reduced in patients with severe renal failure.