We present the case of a patient affected with Williams syndrome (WS), who developed a suspected malignant hyperthermia (MH) reaction to general anes thesia. The proximity to the WS region of the gene en coding the L-type voltage-gated calcium channel a 2/8-subunit (CACNL2A) on 7qll.23-q21.1, previously shown to be closely linked to some forms of MH susceptibility, prompted us to investigate whether this gene is deleted in WS. Linkage studies and fluorescence in situ hybridiza tion analysis demonstrated that the CACNL2A locus is lo calized outside the WS deleted region.