BACKGROUND: Renal failure is a frequent event after coronary artery bypass grafting (CABG). Hemodynamic alterations during surgery as well as the underlying disease are the predisposing factors. We aimed to study intermittent furosemide therapy in the prevention of renal failure in patients undergoing CABG. METHODS: In a single-blind randomized controlled trial, 123 elective CABG patients, 18-75 years, entered the study. Clearance of creatinine, urea and water were measured. Patients were randomly assigned into three groups: furosemide in prime (0.3-0.4 mg/kg); intermittent furosemide during CABG (0.2 mg/kg, if there was a decrease in urinary excretion) and control (no furosemide). RESULTS: There was a significant change in serum urea, sodium and fluid balance in “intermittent furosemide” group; other variables did not change significantly before or after the operation. Post-operative fluid balance was significantly higher in “intermittent furosemide” group (2573 ± 205 ml) compared to control (1574 ± 155 ml) (P < 0.010); also, fluid balance was higher in “intermittent furosemide” group (2573 ± 205 ml) compared to “furosemide in prime” group (1935 ± 169 ml) (P < 0.010). CONCLUSION: The study demonstrated no benefit from intermittent furosemide in elective CABG compared to furosemide in prime volume or even placebo.