We have investigated 13 families, each of which have one member with infantile hypercalcaemia/Williams-Beuren syndrome (IHWBS), for either a germ cell mutation of, or an association with, the calcitonin-CGRP gene. Restriction fragment mapping studies of the calcitonin-CGRP gene using five restriction enzymes (TaqI, Bg/II, PvuII, PstI, and SacI) and region specific probes failed to show any abnormalities of this gene complex. NO association of IHWBS with polymorphism of the calcitonin-CGRP/parathormone locus was found. Therefore, although the aetiology of IHWBS may be caused by a new dominant mutation, there is no evidence to implicate major rearrangements of the calcitonin-CGRP and parathormone genes.