This volume provides a particularly timely survey of invertebrate peptide hormones. Interest has been growing in invertebrate peptide hormones. This interest has focused upon two important and related aspects, both of which are fully covered in this volume. First, many of these peptides are neurohormones with chemical characteristics resembling, sometimes closely, established vertebrate neurohormonal peptides. In this way these findings have had considerable impact on our standing of the origin and evolution of peptide regulators. Second, with the availability of techniques such as HPLC and cDNA probes, which have allowed detailed study of vertebrate peptides, significant advances have been made in our understanding of the physiology and biochemistry of native invertebrate peptides. The volume aims to provide a synthesis between these two aspects of investigative activity. As such, it should have a broad appeal to scientists from a number of disciplines.