With the purpose to avoid the risk of transfusion mediated infection and complication, predeposited autologous blood transfusion was performed. From April 1990 to March 1991, transurethral resection of the prostate (TUR-P) were performed in 27 patients (mean age: 72.5 years) with benign prostatic hypertrophy (BPH). Autologous blood (200-400 ml, mean 244 ml) was predeposited 3 weeks prior to TUR-P in 18 patients (mean age: 73.9 years) and transfused during or just after the operation in 16 (five patients required some homologous blood in addition to their own banked blood). Another three patients were transfused with homologous blood only. The mean values for hemoglobin concentration were 13.7 +/- 0.4 g/dl before blood deposition and 12.8 +/- 0.5 g/dl on the day of operation (recovery rate: 92.5 +/- 2.7%). Although no complication was found in autologous blood transfusion group (11 patients), one case of systemic exanthema and one case of type C hepatitis were observed in homologous blood transfusion group (8 patients). In TUR-P, positive correlations were observed among resected prostate weight (Pro-wt), blood loss (B.) and operation time (Op-T.). Correlation efficient between Pro-wt. and B. was 0.80, that of B. and Op-T. was 0.77 and that of Pro-wt. and Op-T. was 0.85. From these results and ultransomographic measurement of the prostate weight, the amount of blood loss can be calculated preoperatively, there by the amount of blood needed for transfusion will be estimated.(ABSTRACT TRUNCATED AT 250 WORDS)