Anesthesia-induced malignant hyperthermia (MH) is a rare inherited disorder of skeletal muscle. Several mutations in the ryanodine receptor (RYR1) have been found to be causative of MH. The G1021A mutation in the RYR1 is one of the most frequently occurring mutations in European populations. MH normal (165) and MH susceptible (114) North American patients were screened for the presence of the G1021A mutation. This mutation was not found in any of the patients tested. These studies support the absence of this mutation in the normal population. Furthermore, these findings emphasize the importance of viewing the distribution of MH mutations as variable gene pools with frequencies dependent on the geographical location of the population examined.