Patients: Inclusion criteria: All snakebite patients were admitted to the Poison control center of Bach Mai hospital from 01/01/2013 to 31/12/2015 and fullfilled the both following criteria: 1) Patients give the samples or photographs of the culprit snakes to the doctors at the Poison center for the identification of snake species by morphology analysis (the photographs need to bee clear, the posteria views of the hoods must be available if it is the case of cobrabite.