There is increasing commercial interest in the production of functional foodstuffs which have health-promoting properties. Over the last five to ten years, significant progress has been made in the identification and characterisation of bovine milk components that can affect the function of the immune system. This review outlines the major components of bovine milk that have been shown to modulate immune function, and discusses experimental approaches to the identification of various facets of the immune response that are known to be affected by milk-derived proteins.