The short- and long-term effects of prophylactic hemodialysis (HD) immediately after cardiovascular catheterizations on renal function in patients with severe baseline renal insufficiency remain unknown though previous studies reported non-beneficial very-short-term effect in less severe patients.Patients who had pre-procedural serum creatinine (Scr) between 2.5 and 5.5 mg/dl were retrospectively studied. Twenty of them (14 M/6 F, aged 69±2 years) had received prophylactic HD after radiocontrast exposure and constituted the HD group. Another 20 patients were case-matched to the baseline demographics of the HD group and served as the non-HD group. The baseline Scr were 3.9±0.2 and 3.5±0.2 mg/dl, respectively (p=NS). Although the Scr at 3 months was significantly higher in the HD group (4.3±0.3 vs. 3.4±0.2 mg/dl, p=0.02), the absolute and percentage increments from baseline to 3 months (0.4±0.2 vs. 0.0±0.2 mg/dl, p=NS, and 11±5% vs. 1±7%, p=NS, respectively) and 6 months (0.6±0.3 vs. 0.4±0.4 mg/dl, p=NS, and 18±8% vs. 8±10%, p=NS, respectively) were not statistically different. Patients who developed end-stage renal disease requiring permanent HD at 1 year were also similar in both groups (four vs. three, respectively, p=NS).Our study confirmed that prophylactic HD immediately after contrast media administration in catheterizations failed to affect the short- and long-term renal and clinical outcomes even in patients with severe baseline renal insufficiency.