A long-term prognosis was studied in 69 patients with malignant hypertension, followed for an average of 56 months. Overall survival rate was 90% for a 5-year period, although the prognosis was different between two major underlying diseases, namely the 5-year survival was 79% for 33 essential hypertension (EHT) and 100% for 26 chronic glomerulonephritis (CGN); the difference is significant (p less than 0.01). In contrast, the 5-year rate for renal survival, defined as the probability of surviving without hemodialysis, was 37% in all cases. However, there was significant difference in the renal survival between EHT (60% for a 5-year period) and CGN (4% for a 18-month period). Multivariate analyses of the Cox's proportional hazards model revealed that the long-term change in renal function was different between the two groups, namely more rapid deterioration in the CGN group. These results indicate that a long-term prognosis of malignant hypertension is influenced by the underlying diseases and hemodialysis besides antihypertensive treatment may increase survival in malignant hypertension associated with severely damaged renal function.