Abstract A method of obtaining specifically labeled digitoxin-7αT from Digitalis purpurea plants previously fed pregnenolone-7αT is described. The metabolism of digitoxin-7αT by normal rabbits and by rabbits with surgically induced heart failure was investigated. Digitoxin-7αT was injected into both groups of rabbits, and the urinary excretion of radioactivity was evaluated. By means of countercurrent distribution and thin-layer chromatography, a difference in metabolism of digitoxin-7αT between the two groups was observed. The data show that rabbits with heart failure required much longer periods of time to excrete an equal amount of radioactivity as compared with the normal rabbits. Further, although the radiochromatographic patterns of the two groups were qualitatively identical, the profiles showed that in the group with heart failure the conversion of digitoxin-7αT to its relatively more polar metabolites was substantially hindered.