Abstract
Plasma cholinesterase activity has been determined in 1, 029 men. One subject was found to have a consistently elevated plasma cholinesterase activity. Examination of his family revealed that this cholinesterase was probably inherited as an autosomal dominant. In vitro and in vivo studies suggest that the propositus is heterozygous for an enzyme molecule that is more than 3 times as active as the usual cholinesterase. This enzyme seems to provide increased resistance to succinylcholine.