As antineutrophil cytoplasmic antibody positive rapidly progressive glomerulonephritis (ANCA-RPGN) has a high risk of end stage renal failure and is a potentially life threatening disease, early aggressive therapy is recommended. However, aggressive immunosuppressive therapy may lead to immunodeficiency and subsequent mortality in the patients with this disease. Therefore, we need the index of immunodeficiency to cure the disease. To evaluate any risk factors, including therapies, on mortality in ANCA-RPGN, we conducted a retrospective investigation on patient survival in 32 patients with ANCA-RPGN by Kaplan-Meier analysis and the Cox regression model. Fourteen patients were treated with leucocytapheresis (LAP group) and the 18 patients were treated by steroid pulse therapy (steroid pulse group) as initial treatment. The patients were chosen for the different therapies at random. Two patients in the LAP group, and eight patients in the steroid pulse group had died within 6 months. The lymphocyte counts and CD4 cell counts after complete course of therapy were lower in the patients who died than in those who survived in the steroid pulse group. Patient survival was higher in the LAP group than in the steroid pulse group, but did not reach statistical significance. Multivariate Cox regression analysis showed that the factors influencing patient survival were initial serum creatinine, LAP therapy, CD4 cell counts, and lymphocytes at the end of treatment. Age, titer of MPO-ANCA, and percent of glomerular crescents were not found to have an effect on the patient survival. We recommend: that early diagnosis should be established, and immunosuppressive therapy may be done with monitoring of the lymphocyte and CD4 cell count.