We report the high-resolution localization of the human calcitonin/CGRP genes, CALCA, CALCB, and the pseudogene CALCP, to a 220-kb SacII fragment on chromosome 11p15.2-p15.1, using prometaphase fluorescence in situ hybridization (FISH), two-color interphase FISH, and pulsed-field gel electrophoresis analysis. The related islet amyloid polypeptide (IAPP) gene was assigned to human chromosome 12p12.3-p12.1. The results support an evolutionary relationship between the calcitonin/CGRP genes and the IAPP gene and between parts of human chromosomes 11 and 12.