Factors influencing referral of all 304 patients who developed persistent renal failure during one year were studied in the stable Grampian population. The annual incidence of chronic renal failure (CRF) (creatinine > or = 300 mumol/l) was 450/million of the population and of persistent advanced CRF (creatinine > or = 500 mumol/l), 132/million. After excluding those aged > 80 years and those with advanced malignancy, the corresponding incidence figures were 240/million/year and 81/million/year. Only 109 patients (35.8%) were referred to a nephrologist. Patients were divided according to age and coexisting disease into low, medium and high risk groups; 69% of CRF patients in the low, 58% in the medium, and 21% in the high risk group were referred (100%, 88% and 37%, respectively, of the patients with advanced CRF). Two-year patient survival in the low, medium and high risk groups was 100%, 63% and 27%, respectively, in referred patients, and 100%, 48% and 14%, respectively, in non-referred patients. This method of risk stratification identifies patients (particularly those with advanced CRF) likely to have a poor outcome irrespective of referral to a nephrologist. Earlier referral for interventions to delay the progress of the patients' renal and comorbid illnesses has considerable implications for future planning and funding of renal services.