Africanized honey bees and the wasp Polistes versicolor are common insects in Brazil; their venoms are composed of a complex mixture of components which present several biological activities. Stinging accidents are very frequent and are generally followed by important clinical reactions, and even deaths are not uncommon. In the present study, venom was extracted from Africanized honey bees and P. versicolor, and it was biochemically characterized and the antigenic cross-reactivity was investigated by Western blot analysis and specific IgE determination by ELISA in the sera of subjects allergic to each venom. The honey bee venom presented higher phospholipase A2 and hyaluronidase activities than P. versicolor venom, which in turn presented higher lipase, acid phosphatase and esterase activities. A high incidence of false-negatives was also observed during determinations of specific IgE for P. versicolor venom when the kits with venoms from wasps of temperate climates were used, suggesting that the diagnosis of allergy to neotropical wasp venom must take into consideration the clinical history and skin tests.