A reference pattern obtained by crossed immunoelectrophoresis of bovine whey proteins from mature milk, using rabbit antibovine whey antibodies, has been worked out. Out of the total of 29 easily recognizable precipitates, 5 milk-specific proteins and 21 serum proteins were identified. Furthermore, whey proteins which also occur in bovine milk fat globule membrane preparations and in extracts of bovine hair and dandruff were identified. The use of the obtained reference pattern for the identification of milk allergens and the determination of the specificity of human milk precipitins against bovine whey proteins is outlined.