Pollen extracts of the four taxonomically related weeds, Amaranthus retroflexus (Ama r), Chenopodium album (Che a), Kochia scoparia (Koc s), and Salsola pestifer (S. kali) (Sal p), were characterized by various methods including crossed immunoelectrophoresis (CIE), crossed radioimmunoelectrophoresis (CRIE), and SDS-PAGE immunoblotting. The allergen profiles were determined by CRIE and SDS-PAGE IgE immunoblotting. CRIE detected from one to four important allergens, while SDS showed up to four bands that bound IgE from a number of patient sera. CRIE and SDS-PAGE immunoblotting did not recognize the same number of important allergens in the individual weeds, and the number of allergens detected by the two methods differed considerably, suggesting that IgE-binding epitopes may be denatured during SDS-PAGE. However, it was possible to correlate the identity of some of the important allergens detected by CRIE and SDS-PAGE immunoblotting in all four weeds.