This multi-volume set withinInternational Review of Cytologyencompasses the recent advances in the understanding of structure-function relationships at the molecular level of receptors, transporters, and membrane proteins. Several diverse families of membrane receptors/proteins are discussed with respect to the molecular and cellular biology of their synthesis, assembly, turnover, and function. Included are such receptor superfamilies as G-proteins, immunoglobulins, ligand-gated receptors, interleukins, and tyrosine kinases as well as such transporter/protein families as pumps, ion channels, and bacterial transporters. Each section of each volume features a "perspectives/commentary" chapter which includes comments on the recent advances and predictions on new directions. Written by acknowledged experts in the field, this volume, 137B, highlights the recent developments in receptors.