Objective To discuss whether radiocontrast nephropathy can be avoided by prophylactic hemodiafiltration immediately after the administration of contrast media in patients with impaired renal function. Methods We retrospectively analyzed 56 patients(1995～2003year in-hospital) with impaired renal function who received contrast medium injection. Patients were assigned to either hemodiafiltion (n = 26) or routine treatment (n = 30) after parenteral low-osmolality contrast media. The renal function、the rate of in-hospital events（pulmonary edema、 myocardial infarction 、stroke）、In-hospital mortality and temporary renal-replacement therapy freguency were observed. Results The incidence of contrast-agent induced nephropathy was 47 percent in the routine treatment group, and 8 percent in the hemodiafiltration treatment group; Temporary renal-replacement therapy (hemodialysis or hemofiltration) was required in 30 percent of the control patients and in 8 percent of the patients in the hemodiafiltration group(P<0.05). The rate of in-hospital events was 4percent in the hemodiafiltration group and 50 percent in the control group (P<0.01). In-hospital mortality was 4 percent in the hemodiafiltration group and 13 percent in the control group (P<0.05). Conclusion In patients with chronic renal failure who are undergoing percutaneous coronary interven-tions, prophylactic hemodiafil-tration therapy appears to be effective in preventing the deterioration of renal function due to contrast-agent-induced nephropathy and it's may improve prognosis effectively.