The paper outlines well recognized growth factors in milk (colostrum and during lactation) like the IGF-family; epidermal growth factor; transforming growth factors a, beta; tumor necrosis factor; basic fibroblast growth factor and platelet derived growth factor The origin of these factors is discussed. The IGF-family may be of greater benefit to the newborn calf in contrast to other species where EGF seems to be the dominating and important factor. However, the primary role of the measured growth factors may be related more to the proliferation and maintenance of the lactating gland itself.