Antigenic cross-reactivity was studied among the components of venoms from nine species of the genus Bothrops using species-specific antivenoms . Sera titration by DOT-ELISA detected similar levels of antibody when either homologous or heterologous antigens were used. Transblotted antigens, after SDS-PAGE fractionation, were also revealed by homologous and heterologous antivenoms . Antigens with mol. wt greater than 30,000 seemed to be the most cross-reactive . Antigens of about 24,000 mol. wt were poorly immunogenic. Antigens between 14-18,000 mol. wt cross-reacted only with B. moojeni, B.jararacussu, B. neuwiedi and B. pradoi venoms. Neutralization of the lethality of B. jararaca venom was observed by homologous and heterologous antivenoms .