To investigate whether the column material employed in size-exclusion high-performance liquid chromatography (HPLC) influences the allergenic activity and antigen/allergen patterns of allergen extracts, the molecular weights of a mite and a birch pollen allergen extract were determined using a Bio-Sil TSK 250 column with a guard column. The allergenic activities were measured by RAST inhibition and the antigen/allergen patterns were determined by crossed (radio)immunoelectrophoresis. The original extracts and the corresponding eluates after HPLC runs showed the same allergenic activity and the same number of antigen/allergen precipitation lines. Only slight differences in the peak heights of some precipitates were observed.