In recent years, our understanding of the many physiological, biochemical, and molecular functions and attributes of vitamin D-binding protein (DBP) has seen exciting and significant advances. Since its identification in 1959, many important functions of this abundant serum protein have been discovered. These range from the transport of vitamin D metabolites to possible roles in the immune system and host defense. With these discoveries, many questions regarding the biology of DBP have been raised and many remain to be answered. Our current understanding of the classic and less-recognized activities of DBP is discussed here.