The calcitonin family of peptides, which includes calcitonin, two calcitonin-related gene peptides (CGRPs), adrenomedullin, and amylin, share a disulfide-bonded loop, an amphipathic a-helix, and an amidated C-terminus. The peptides influence a variety of physiological effects, including vascular tone, food intake and bone metabolism. The biological effects of the peptides are mediated by two class B GPCRs, CT receptor (calcitonin receptor) and CL receptor (calcitonin receptor-like receptor). The pharmacology of the CT and CL receptors is strongly influenced by their association with a family of three receptor activity modifying proteins (RAMPs), which are 14-17 kD single pass transmembrane proteins. CGRP (calcitonin gene-related peptide) induces vasodilation, and its activity is primarily mediated by CGRP1, composed of CL in complex with RAMP1. As a consequence of its role as a vasodilator, CGRP acting via CGRP1 appears to play an important role in hypertension.