Allergen-specific monoclonal antibodies (MoAb) are of growing importance in allergen standardization, especially in setting up assays to measure quantitatively allergen content in therapeutic extracts and to establish secondary standards. MoAb are useful in measuring allergenic indoor pollution and in monitoring allergen clearance in cases of recommended allergen avoidance. In applied research MoAb are valuable tools in allergen purification providing primary standards. As a source for developing MoAb of the second generation they open new perspectives.