Although the different vespid species of the genus Polistes are found all over the world, studies about allergy sensitization to these species have been made mainly in North America. We studied the specific IgE in a large group of sera from patients sensitized to Polistes dominulus (PD) and determined the crossreactivity with another important European Polistes (P. gallicus [PG]) and with five American relevant species of this genus: P. exclamans (PE), P. fuscalus (PF), P. metricus (PM), P. annularis (PAN) and P. apachus (PAP). Studies indicated that 96.7% of sera with IgE positive to PD were positive to PG. No case positive to just PG was found. The comparison of these two European species with the American relatives indicated that most cases were positive to all the insects although there were significant differences in the radioallergosorbent test (RAST) value. These results were confirmed by RAST inhibition studies, and indicate that although the European and American species are closely related, species specific allergenic differences exist. These data suggest that in vivo studies should be carried out in order to determine the sensitivity and specificity of the European venoms compared with the American species.