BACKGROUND Dextran is an effective plasma expander but also a potential anticoagulant. This article attempts to establish the clinical significance of any increased intra-operative blood loss associated with the use of dextran 70 during transurethral resection of the prostate (TURP). METHODS The blood loss was measured in used irrigating fluid by a photometer in 800 patients undergoing TURP. In 154 of them, 500-1,000 ml of 6% dextran 70 was given for volume replacement. A regression model was used to test for interactions between the use of dextran and the operative parameters that correlated independently with the blood loss. RESULTS The bleeding varied between 10 and 3,825 ml (median 323). Operative parameters correlating to the blood loss were: weight of the prostatic resectate, operating time, irrigating fluid absorption, and systolic arterial blood pressure. The result of this regression analysis indicated that dextran did not increase the blood loss. Neither did the prostatic weight and operating-time-corrected blood loss increase when dextran was infused. CONCLUSIONS There was no indication that dextran 70 given within the recommended dose range increases the blood loss during TURP.