The calcitonin family of bioactive peptides comprises of calcitonin, amylin, two calcitonin-gene related peptides (CGRP1, and CGRP2) and adrenomedullin (ADM). Amylin is a 37-aa peptide produced in the pancreatic beta- cell secretory granules and is co-released with insulin. Amylin also has CGRP-like effects on bone metabolism. Amylin has specific binding sites in the CNS and it may regulate gastric emptying and influence carbohydrate metabolism. The calcitonin family peptides probably act through G-protein coupled membrane receptors. Recently, a homolog of calcitonin receptor, CRLR (calcitonin- receptor-like receptor human 461 aa; rat/mouse 463 aa) was identified. It is now shown that CRLR can function as either a CGRP receptor or an ADM receptor, depending upon which members of a new family of proteins called receptor activity modifying proteins (RAMP1-3) are expressed.