Previous studies suggested that membranoproliferative glomerulonephritis (MPGN) type II has a worse renal survival and an unacceptable risk of recurrence post transplantation. We hypothesised that other factors may determine this risk. We analysed all cases (n=70) of MPGN diagnosed by renal biopsy in Ireland from 1972 to 1995. We used Cox regression analysis to determine factors that were independently predictive of renal failure. MPGN II had more crescent formation and mesangial proliferation (P<0.05). Mean follow-up duration was 13.8 years, during which time 41 (58.6%) developed end-stage renal failure (ESRF). The median time to ESRF was 8.3 years (95% confidence interval 5.7-10.9) and 5-, 10-, and 20-year probabilities of ESRF were 32, 54, and 70%, respectively. Multivariate analysis revealed that severity of interstitial fibrosis (P<0.05), crescent formation (P<0. 01) and mesangial proliferation (P<0.05) were independently associated with ESRF. Decade of diagnosis, age, MPGN type, and creatinine or complement level at baseline did not predict renal survival in this model. In 21 (49%) of the 43 renal transplants, MPGN recurred. Younger age at initial diagnosis (P<0.01) and the presence of crescents on the original biopsy (P<0.005) were independently associated with recurrence on multivariate analysis. MPGN type was not associated with recurrence in this model. Contrary to previous reports, after controlling for crescent formation, MPGN II was not associated with more ESRF or recurrence in the allograft. It is therefore the more aggressive glomerular changes associated with MPGN II, rather than the disease type per se, that determine outcome.