The present article reviews the current knowledge on incidence, epidemiology, pathophysiology, clinical features, diagnosis and prognosis of accidents by poisonous snakes of Brazil. Bothrops, Crotalus, Lachesis and Micrurus are the genera responsible for more than 100 deaths per year. With the exception of Micrurus, all cause clotting disturbance; Lachesis and Bothrops cause destruction of the tissue at the region of the bite, Crotaius and Micrurus cause failure at the neuromuscular junction and only Crotalus cause systemic myotoxicity. The clinical aspect is normally sufficient for diagnosis, except for the distinction between bothropic and lachetic accidents. Treatment with the specific heterologous serum must be started precociously by endovenous route. It is also important to maintain the patient hydrated and, in the case of Micrurus bites, adequate aereation must be applied.