The information available regarding the chemical structure of RBP, the structure of the RBP gene, and the expression of the RBP gene has expanded dramatically in recent years. Still many questions concerning RBP remain to be answered. The longstanding and important questions concerning the possible existence and the biochemical characteristics of the RBP cell surface receptor are in need of resolution. The factors that regulate RBP secretion from the liver still remain to be fully elucidated. Additional information concerning the physiological role of RBP synthesis in extrahepatic tissues is needed. Considering what is now known, it is clear that in the future much intense research will be required before the many important questions regarding the structure, synthesis, secretion, and physiological roles of RBP can be answered.