From somewhat enigmatic beginnings 40 years ago, guanylate cyclase research has emerged to occupy a position of prominence in the study of signal transduction. Guanylate cyclase has several intriguing features, including existence in two major forms, membrane and soluble, each independently regulated by distinct mechanisms. The membrane form gives rise to a fascinating signal transduction story important to both peptide hormones and sensory neurons. This volume covers the evolution of the field, peptide hormone receptor work, membrane guanylate cycles, related retinal diseases, and the biochemistry and physiology of the soluble form. The 16 chapters are written by leaders in the field.