Abstract: The effects of various soluble extracts of Ascaris suum on human blood coagulation were studied. The extract of whole worm could prolong recalcification time (RT) and kaolin-activated, partial thromboplastin time (KPTT), but did not alter prothrombin time (PT), indicating that the intrinsic pathway of blood coagulation was inhibited by this extract, but the extrinsic pathway was not affected. Whole worm extract inhibited platelet aggregation induced by ADP, but did not influence the one induced by adrenaline. Neither whole worm extract nor body fluid caused fibrinolysis. In KPTT assays with three dif-ferent extracts, cuticle extract exhibited the strongest anticoagulant activity, while whole worm extract and body fluid much less so. These data suggested that anticoagulants of ascaris mainly exist in the cuticle,