Toxicity screening of a newly developed oral heparin derivative was carried out in twelve male cynomolgus monkeys (Macaca fascicularis), composed of three treatment and vehicle control groups. A newly orally active heparin derivative, developed by Seoul National University, was given to the treatment group at three doses with low (12.8 mg/kg), medium (89.6 mg/kg) and high (640 mg/kg) doses for 14 days. A treatment group did not show any change in body weights, hematological parmeters (e.g., RBC, WBC, platelet, PDW, MPV, etc.) and serum biochemical parameters (e.g., AST, ALT, BUN, etc.) for 2 weeks compared with those of the vehicle control group. These findings indicated that the oral anticoagulant drug, a newly developed oral heparin derivative, did not have any toxic effect for 2 week in this study. The present study will be valuable in the proper interpretation for non-clinical study using cynomolgus monkeys in the development of a new drug of heparin derivative.