Four hundred and fifteen cases of bites by adult Bothrops jararaca (group A) were admitted to the Hospital Vital Brasil between 1981 and 1987. These cases were compared to 562 cases of bites by young snakes of the same species (group B) during the same period and at the same hospital. In group B blood incoagulability was more frequent when compared to group A. However in group A bites in the leg, use of tourniquet, tecidual damage (blister, necroses and abscess), were more frequent when compared to group B. The doses of sero given for the group A was greater when compared to group B. Accidents month distribution, dates available were for the patients admitted between 1975 and 1988. The accidents were more frequent in the first and at the end of the year. In the first months of the year for the young snakes and mainly at the end of the year for the adult snakes.