Various haemostasis disorders can occur following snakebite. Almost all ophidian species that are responsible for serious, even lethal, human envenomations are concerned. Venoms of these snakes are rich in proteins interfering with haemostasis, including many enzymes. These proteins can be classified in four groups according to their action. The haemorrhagins induce capillary permeability disorders. The proteins disturbing the primary haemostasis can activate as well as inhibit platelets: phospholipases A2, serine proteases and metalloproteinases, L-amino-acido-oxydases, phosphoesterases, disintegrins, C-type lectins, dendropeptin, agregoserpentin, thrombolectin. The proteins interfering with coagulation are separated into procoagulant proteases (prothrombin activator, thrombin-like enzymes, factor X and factor V activators) and anticoagulant proteases (factor IX and X inhibitors, protein C activator, anticoagulant phospholipases A2). The venom components acting on fibrinolysis are the fibrinolytic enzymes and the plasminogene activators. The clinical consequence of these mechanisms is a local as well as diffuse haemorrhagic syndrome. A hypofibrinogenemy, even an afibrinogenemy is frequently noted. Other haemostasis parameters are disturbed: PT collapse, a patient's ACT several times higher than the control and non-systematic thrombopenia. Ophidian venoms take part in many medical, diagnostic or therapeutic, applications in medicine. Currently, the antivenomous immunotherapy is the only efficient treatment in these haemorrhagic disorders.