The objective of this study is to analyze the tolerance and efficacy of the subcutaneous administration of a reduced 2,500-unit low-dose unfractionated heparin given for an efficacious, yet Asian population-sensitive, prophylaxis for deep vein thrombosis and fatal pulmonary embolism. Eighty-seven Japanese patients were operated on either for abdominal or pelvic complications or both, as well as for gynecologic conditions including ovarian, cervical, and corpus cancers. Thirty-two of the patients were administered the experimental low dose of unfractionated calcium heparin for prophylaxis. The 2,500 units of low-dose unfractionated heparin were given subcutaneously 2 h preoperatively and again 12 h postoperatively. Other standard methods of mechanical prophylaxis, including graduated compression stockings and intermittent pneumatic compression, were performed. Fifty-five of the patients were not administered heparin, but did receive the same standard mechanical graduated compression stockings and intermittent pneumatic compression prophylaxis. We compared the surgical and postsurgical complications noted for low-dose unfractionated heparin patients with the results of those who received no heparin prophylaxis and analyzed this data using the Mann-Whitney U-test. There was no significant difference in the mean of the blood loss volumes. There were also no significant differences found in the perioperative bleeding complications between the two groups. However, three (3/55; 6%) of the patients in the no-heparin group suffered a symptomatic pulmonary embolism, although none were fatal. There were no pulmonary embolism onsets in the heparin prophylaxis group. We feel that we have provided evidence that several serious complications, such as perisurgical hemorrhage, deep vein thrombosis, fatal pulmonary embolism, and increased postoperative recovery times, can be prevented by prophylaxis with 2,500-unit low-dose unfractionated heparin.