Pure venom from Solenopsis invicta was collected by having the insects sting into a capillary tube. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that three major protein bands were present in the venom. A prototype commercial extract was compared and found to contain the three major venom proteins and additional components as well as high potency and specificity by RAST. Immunoblot studies were performed with sera from allergic individuals with blots prepared from denatured SDS-PAGE gels and from two types of nondenaturing gels. The nondenaturing systems demonstrated the presence of two major allergens and three other allergens, each reacting with a third of the sera. Three of the allergens detected in SDS-PAGE blots were of identical mobility to the three major proteins in the pure venom sample. IgE binding to the SDS-PAGE blots was significantly less than that to nondenaturing blots, suggesting that much of the allergenic activity is conformation dependent.