During a period of 19 months (March 1986 - September 1987), 22 cases of snake bites caused by Bothrops moojeni in São José do Rio Preto, São Paulo (South-east Brazil) were studied. The animals have their lenght measured and two groups were constituted: group I - 9 cases with lenght between 30 and 53 cm and group II - 13 cases with lenght between 80 and 147 cm. Our results revealed: 1. the local effects - pain and swelling - were frequently mild in group I; 2 - non-clotting blood (bed-side test) occured in two groups, a little more frequently in group I; 3. local complications - necrosis, compartment syndrome and infection - occured in more then a half and exclusively in group II, in spite of larger and faster antivenom therapy. We have concluded that larger Bothrops moojeni produced great increment in swelling, necrosis and infection and mild decrement in coagulation action.