A retrospective analysis was made of 191 uraemic patients whose first arteriovenous fistula was constructed in the period 1972-1978. Only direct-type lower forearm fistulas were considered. The aim was to identify and evaluate factors influencing fistula patency rate. Evaluation was done by simple and multiple regression analyses and by actuarial life table computation. Early failure of fistula occurred most frequently in patients with diabetes, peroperative blood pressure less than 110 mmHg, small-calibre veins and/or less than maximal uraemia. The early failure rate among patients with low peroperative blood pressure was 53%, and in the other patients 24%. Among patients with serum creatinine higher than 1 140 mumol/l the corresponding figure was 11%, while in those with lower values it was 35%. Long-term fistula patency was influenced by sex (with advantage to males), by diabetes or diabetic vasculopathy, and seemingly be a tendency to hypotension in some patients. Direct-type forearm fistula may well be utilized in patients with narrow veins. The operation should not be performed long before induction of haemodialysis. This is because some of the fistula's lifespan will be wasted if it is created too soon, and because the early failure rate is lower in patients with advanced uraemia. The analysis also reflects problems that can be anticipated, as diabetics constitute an increasing proportion of patients requiring vascular access.