We studied the protein-stabilizing properties of sucrose, in the extraction medium, on the composition and stability of ryegrass (Lolium perenne) pollen extracts. The effect of 0.5 M and 1 M sucrose was assessed in the presence and absence of 0.5% phenol, which is commonly used as a disinfectant in industrially prepared allergenic extracts. In the absence of phenol, sucrose improves the stability of extracts during storage, but it has little influence on the extraction process. In the presence of 0.5% phenol, however, both the quality of fresh extracts and the stability are greatly improved by 0.5 M and by 1 M sucrose, as shown by electrophoresis, immunoblotting, and RAST-inhibition experiments. The protection afforded by sucrose against the degrading effect of phenol is particularly evident for the major allergen Lol p 1 and for a set of basic allergens. In this respect, sucrose has been found to be superior to glycerol, on an equimolar basis. One may envisage the use of 0.5 M sucrose in allergenic extracts for intradermal testing and immunotherapy.