INTRODUCTION: The low-molecular-weight heparins have been demonstrated to have antiangiogenic effects in various assays. We aimed to demonstrate and compare the antiangiogenic effects of four types of commercially available low-molecular weight heparins in the chick embryo chorioallantoic membrane model. MATERIALS AND METHODS: The antiangiogenic efficacies of bemiparin, enoxaparin, nadroparin, and tinzaparin were examined in vivo in the chick chorioallantoic membrane model. Drug solutions are prepared in three different concentrations (100 IU, 10 IU, or 1 IU/10 μl). For each set of experiment twenty fertilized eggs were used. The decrease of vessel formation is examined and scored according to previous literature. RESULTS: Bemiparin, enoxaparin, nadroparin, and tinzaparin sodium all have antiangiogenic effects on chick chorioallantoic membrane at the concentration of 100 IU/10 μl. This effect was also observed in 10 IU/10 μl concentrations of nadroparin and tinzaparin. CONCLUSIONS: The low molecular weight heparins studied have obvious antiangiogenic effects. There may be a difference in the potency of the drugs that could have a significant implication for further clinical research.