Homeostasis, growth and reproduction in crustaceans are under endocrine control as is established in other animals. The identification of crustacean hormones and elucidation of mechanisms of hormonal regulation have been pursued extensively. Mechanisms are found to be partly similar to, but also considerably different from those in insects, although both groups of animals are arthropods. Molting in insects, for example, is positively regulated by prothoracicotropic hormone (PTTH), which is secreted by the brain/corpora allata complex and stimulates the prothoracic glands to promote the synthesis and secretion of ecdysteroids. On the other hand, molting in crustaceans is negatively regulated by molt-inhibiting hormone (MIH), which is secreted by the X-organ/sinus gland complex and suppresses the Y-organs from synthesizing ecdysteroids during the intermolt period. Therefore, it is rather difficult to fully elucidate physiological mechanisms in crustaceans based only on the results obtained in insects. Using experimental evidence, we have thus far looked into the roles of crustacean eyestalk hormones and androgenic gland hormone (AGH). Various eyestalk hormones have been isolated from the sinus glands and characterized: e.g., crustacean hyperglycemic hormone (CHH), MIH, vitellogenesis-inhibiting hormone (VIH), red pigment concentrating hormone (RPCH) and pigment dispersing hormone (PDH). CHH, MIH and VIH are structurally similar, forming the CHH-family. Insects also possess molecules similar to CHH, RPCH and PDH, but their functions are different. In addition, AGH has been studied mainly using terrestrial isopods. Here, we describe the present state of our understanding of the structure and function of these peptide hormones, and discuss future perspectives.