We report the use of dopamine in renal doses (5 micrograms/kg/min) to prevent contrast induced nephropathy (CIN). Forty patients with diabetes mellitus who were undergoing coronary angiography were randomly divided into two groups. Gr I (20 patients) was infused with dopamine starting 30 min before cardiac catheterization and continued for 6 h thereafter. Gr II (20 patients) did not receive dopamine. Baseline blood chemistry was performed before catheterization and then repeated 24 h after the procedure. The mean age and sex distribution were similar in both the groups. Urograffin (76%; 120-150 ml) was used in all the cases. The mean serum creatinine and blood urea nitrogen (BUN) levels in Gr I patients before catheterization were 1.5 +/- 0.32 mg % and 16.3 +/- 8.05 mg %, respectively. The corresponding values for Gr II were 1.52 +/- 0.68 mg % and 19.6 +/- 13.4 mg %, respectively. After angiography, Gr I patients did not show significant changes in renal parameters (serum creatinine, 1.37 +/- 0.25 mg % and BUN, 14.7 +/- 5.5 mg %) while Gr II patients showed a significant rise (serum creatinine, 1.96 +/- 1.2 mg % and BUN, 23.25 +/- 12.7 mg %; P = 0.01 and P = 0.05, respectively). Ten patients in Gr II (50%) developed a 25% rise in serum creatinine levels within 24 h of injection of the contrast. None of the patients developed renal failure severe enough to warrant dialysis. Hence alterations of renal function are common after cardiac catheterization. Dopamine in renal doses appears to be an effective means to prevent deterioration in renal function induced by contrast.