ABSTRACT Whey protein, a high-biological-value protein from milk, is available with and without immunoglobulins. The possibility of providing passive immunization through food is unique to mammals, who receive it through colostrum at birth. Colostrum contains both immunostimulatory and immunosuppressive immunoglobulins. Later, the mammals are able to make their own immunoglobulins, but in time of illness that ability may become impaired. Some of the whey proteins contain bovine immunoglobulins, which are similar to human immunoglobulins. This type of whey may be of clinical importance to patients who are immunocompromised. However, all whey proteins are rich in cysteine and glutamate. These serve as precursors of glutathione, a potent antioxidant, which is needed in greater quantities during stress. In this review, the benefits of consuming whey protein with and without immunoglobulins are examined. Characteristics of these products are discussed, and an account is given of supportive studies using the whey containing immunoglobulins in the clinical setting. Patients with acquired immunodeficiency syndrome and cancer are used as examples. Finally, a guide on use of whey protein is provided.