Background and objectives: Malignant hyperthermia (MH) is a pharmacogenetic disease that causes abnormal hypermetabolic reaction to halogenated anesthetics and/or depolarizing muscle relaxants. In Brazil, there is a hotline telephone service for MH since 1991, available 24 hours a day in São Paulo. This article analyzes the activity of the Brazilian hotline service for MH in 2009. Methods: Prospective analysis of all phone calls made to the Brazilian hotline service for MH from January to December 2009. Results: Twenty-two phone calls were received: 21 from the South/Southeast region of Brazil and one from the North region. Fifteen calls were requests for general information about MH. Seven were about suspected MH acute episodes, two of which were not considered as MH. In fi ve episodes compatible with MH, all patients received halogenated volatile anesthetics (2, isofl urane; 3, sevofl urane) and one also used succinylcholine; there were four men and one woman, with a mean age of 18 years (2-27). The problems described in the fi ve MH episodes were tachycardia