Low molecular weight dextran (dextran 40) has been widely used not only as a plasma expander and blood flow improver in various diseased or shock states, but also to prevent postoperative thromboembolic complications, especially in major operations such as vascular and hip surgery. Despite the fact that the drug can be administered with few complications, it can produce serious lifethreatening anaphylactoid reactions, although this occurs very rarely. The authors retrospectively investigated 89 patients, who developed a shock state perioperatively, out of 5267 patients in the operating room from April 1975 to June 1980 at the Jeonbug National University Hospital. Eight patients out of 89 developed a shock state with flushed skin, goose skin, bronchospasm, conjunctival injection and chest pain. These symptoms and signs were thought to be due to an anaphylactoid reaction to dextran 40. During this period of time, 2023 dextran 40 units were administered, so that the incidence of dextran induced anaphylactoid reaction was up to 0.40%. This is more than 10 times as much as reported by some investigators.