In a study in seven large renal units in England, the morbidity and mortality of all patients starting continuous ambulatory peritoneal dialysis (CAPD) and haemodialysis during 1983-85 were monitored prospectively over a 4-year period and related to reasons for choice of therapy and potential risk factors. 610 new patients (median age 52 years, range 3-80 years) started CAPD; 16% had diabetes mellitus and 21% cerebrovascular or cardiovascular disease. 329 patients (median age 48 years, range 5-77 years) started haemodialysis; 7% had diabetes mellitus and 17% cerebrovascular or cardiovascular disease. The Kaplan-Meier patient survival estimates at 4 years were 74% for haemodialysis and 62% for CAPD; technique survival figures for the same period were 91% for haemodialysis and 61% for CAPD. Cox's proportional hazards regression analysis showed that cerebrovascular/cardiovascular disease, age over 60 years, and diabetes mellitus were important predictors for survival in CAPD patients; there were no risk factors associated with permanent change to haemodialysis. In the haemodialysis group early change to CAPD was associated with presence of cerebrovascular or cardiovascular disease. The major cause of drop-out in both groups was transplantation. The mean length of hospital admission was 14.8 days per patient-year for CAPD and 12.4 days per patient-year for haemodialysis.