Ten healthy young volunteers (mean age 28 years) and 24 patients (mean age 54 years) suffering from various degrees of chronic renal failure received an infusion of 400 mg pefloxacin (1-ethyl-6-fluoro-1, 4-dihydro-7-(4-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid) over 30 min. The blood and urine levels of pefloxacin and of the two metabolites pefloxacin-N-oxide and norfloxacin were determined using the HPLC method. Blood levels were taken after periods of 0, 60, 120, 180, 360, 600, 720, 1440, 2880, 3360 min, and in patients suffering from renal insufficiency also after 4320 min. The urine was collected and analyzed during the periods of 0-2, 2-4, 4-10 (12) h and then in longer periods up to 72 h. In all subjects, the glomerular filtration rate (GFR, by chrome-51-EDTA) and the plasma creatinine level were determined. Effective levels against bacteria lying in pefloxacin's spectrum can be found in the plasma for about 1.5 days and in the urine for about 2.5 days. Patients suffering from chronic renal failure have pefloxacin plasma levels which beyond 24 h are higher than in healthy persons. This can be explained by both: impaired renal and extrarenal elimination. The volume of distribution of the volunteer and the patient group does not differ significantly. Therapeutic urine levels could be found in patients up to 48 h after end of infusion. Even in patients requiring regular hemodialysis, therapeutic urine levels were found up to 24 h (if urine could be produced at all). The substance therefore is a suitable remedy for urinary infections in dialysis patients as well.(ABSTRACT TRUNCATED AT 250 WORDS)