Pollen was collected from different cultivated varieties ofDactylis glomeratain 1986, 1987 and 1988 and compared with an undifferentiated stock ofDactylis glomeratapollen harvested and stored dry at +4°C since 1981. The allergen content of the crude pollen extracts was established on the basis of the IgE antibodies from the sera of three different patients allergic to grass pollen, using the nitrocellulose immunoprint technique following isoelectric focusing (IEF) and separation in agarose gels. Coomassie blue and silver staining patterns were also compared. They showed some marked differences in the isoelectric points of the constituants of these extracts. Using this major allergen recognition by patient sera as a selection criteria we were able to delimit 8Dactylisvarieties with low or undetectable Dac g IV allergen amounts and 7 varieties which contained this allergen. Two other allergens used as markers enabled us to suggest a kind of taxonomy, based upon the allergen presence, of these 15 varieties. The effect of the storage temperature was studied for 8 different varieties kept at +4°C, -20°C and -40°C. The allergen recognition and silver staining patterns after IEF separation of the crude pollen extracts revealed a selective persistance of some constituants and the disappearance of others at +4°C. The effect of freeze-drying was also analysed in the same way. Finally the pollen constituants of oneDactylis glomeratavariety, harvested in 1986 and 1987 and kept at different temperatures were compared using the same techniques.