Abstract: Changrolin, 4-3′, 5′-Bis (Pyrrolidinyl) methyl-4′-Hydroxy-anilino quinazoline, is an antiarrhythmic drug. Its intracellular distribution in myocardium of rabbits has been studied by differential centrifugation. The components of cells were fractionated into three parts, nuclear, mitochondrial and supernatant fraction. Most of the drug was found in the supernatant fraction. Next is the nuclear fraction. Physico-chemical studies demonstrate that the binding of Changrolin to the nuclear fraction is a rather "physical" process. Part of the drug in the supernatant fraction has been proved to be associated with the cytoplasmic proteins.