Crustacean hyperglycemic hormone (CHH) was isolated from sinus glands of Carcinus maenas, and its primary structure was determined by manual microsequencing, using the DABITC-PITC double-coupling method. The neurohormone consists of 72 amino acid residues (8524 Da). Three disulfide bridges are present and both the N-and C-terminus are blocked.CHH does not show significant sequence homology to any known peptide hormone or protein.Amino acid sequence; Crustacean hyperglycemic hormone; Neuropeptide; (Carcinus maenas)