The calcium-dependent binding of phenothiazine drugs to calmodulin (Levin, R. M. and Weiss, B. (1977) Mol. Pharmacol. 13, 690-697) has been utilized to develop a rapid purification procedure for calmodulin based on fluphenazine-Sepharose affinity chromatography. Calmodulin from plant, a fungus, porcine brain and the coelenterate, Renilla reniformis, were easily purified by the calcium-dependent binding of calmodulin to fluphenazine-Sepharose. © 1979.