Abstract Malignant hyperthermia occurs in man and pigs as a hereditary disorder notably as a complication of halotane-induced anaesthesia. It involves an abnormality in the metabolism of Ca 2+. A search was made for abnormalities of calcium-binding proteins. Troponin C from normal pig muscle was found to differ in 2 of 159 amino acids from rabbit Tn C and 3 from man. No differences between normal and abnormal pig muscle were found. Two-dimensional electrophoresis of red cell calmodulin from normal and abnormal pigs also failed to demonstrate a difference.