Abstract: Following an oral dose of 250 mg of clarithromycin to 14 healthy adult male volunteers, renal clearance and urinary excretion of the drug and that of endogenous creatinine were determined. Before drug administration control samples and after drug administration blood and urine samples were collected, at predetermined time periods. The plasma and urine samples were assayed for endogenous creatinine by spectrophotometric methods and clarithromycin by microbiological assay. Mean ± SE values for the blood and urine pH mean were 7.9±0.08 and 5.7±0.17 respectively. The rate of urine flow (diuresis) was 0.019±0.003 ml/min/kg and creatinine was cleared at rate of 1.95±0.164 ml/min/kg of body weight. Average±SE value for clarithromycin clearance was 0.54±0.08ml/min/kg and mean±SE value for clearance ratio was 0.31±0.061. Cumulative amount of dose excreted until 24 hrs. showed an average value 6.1±0.76 percent. A significant positive correlation between diuresis and renal clearance of clarithromycin indicate the back diffusion or reabsorption of the drug.