Toxicity screening of a newly developed oral heparin derivative were carried out in 6 male cynomolgus monkeys (Macaca fascicularis), composed of a treatment group and vehicle control group. A newly orally active heparin derivative, developed by Seoul National University, was once given to treatment group at dose of 500 mg/kg. A treatment group did not show any change in body weights, hematological parameters including platelet-related varivables (platelet, PDW, PCT, MPV) and serum biochemical parameters (e.g., AST, ALT, BUN, etc.) for 2 weeks compared with those of vehicle control group. We also confirmed the maximum plasma concentration (Cmax, 1.73 IU/ml) and the time (Tmax, 1 hr) to reach Cmax. The present study will be valuable in the proper interpretation for nonclinical study using cynomolgus monkeys in the development of new drug of heparin derivative.