Venoms from six species of ground dwelling yellow jackets of the genus Vespula were studied by direct and inhibition of RAST. Significant differences were found among the various species. Reactivity of patients showed significant correlation with insect distribution with the exception of some patients from the far west. The immunologic relationships observed among the venoms correlated well with the current phylogeny, which is based upon morphologic, behavioral and ecologic studies. The correlation with isoenzyme studies that have recently been reported was less complete. Individual patients exhibit highly significant differences in their reactivity to the various species, in many cases comparable to the differences seen in reactivity to yellow jackets and aerial hornets (Dolichovespula).