The results obtained in these studies show that certain mugwort allergens are extracted after 5 min extraction time and that there is little difference whether phosphate-buffered saline or NH4HCO3 is used as extraction buffer. An extraction time of 1 h appears to be sufficient for a quantitative extraction of the main part of the allergens present. When the extracts are dialyzed, cathodic antigens/allergens are lost. Addition of thiourea leads to a reduction in the coloured matter of the extract, but not in a sufficient degree to recommend the compound to be included in the extraction procedures of allergens from mugwort pollen. A few allergens are heatresistant, and as these fractions are richer in carbohydrate than equivalent fractions not being heattreated, these allergens might be of glycoprotein nature. Structural features of the carbohydrate moiety are also described as well as the total amino acid composition of the protein moiety.