Radiographic contrast agents can cause acute decrease in renal functions. It is thought that anti-oxidant acetylcysteine can prevent contrast nephropathy. Fifty patients planned to undergo elective diagnostic coronary angiography with serum creatinine values above 1.3 mg/dL were included in the study. Acetylcysteine was given orally at a dose of 600 mg twice daily, on the day before and on the day of administration of contrast agent in the acetylcysteine group (n=25). Acetylcysteine was not given to the control group (n=25). Saline (0.9%) was given intravenously at a rate of 1 mL/kg/h for 12 hours before and 12 hours after administration of contrast agent. Contrast nephropathy was detected in 3 of 25 patients (12%) in the acetylcysteine group and 2 of 25 patients (8%) in the control group (P>0.05). Contrast nephropathy was developed in 2 of 4 patients (50%) with baseline serum creatinine concentrations above 2.5 mg/dL, whereas it was developed in only 3 of 46 patients (6.5%) with baseline serum creatinine concentrations below 2.5 mg/dL (P=0.04). It was detected that in patients planned to undergo elective diagnostic coronary angiography with renal dysfunction, oral acetylcysteine and hydration before the procedure was not more effective than hydration alone in the prevention of contrast nephropathy. High baseline serum creatinine values were detected as a risk factor for development of contrast nephropathy.