Abstract Treatment of Bacillus subtilis and Bacillus megaterium cells by ordinary procedures failed to extract any soluble cytochrome from the cell. Sonoration produced small fragments which contained the cytochrome complement and were sedimentable in a centrifugal field of 144,000 × g . Difference spectra of such particles showed absorption maxima at 599, 557, 552, 530, and 428 mμ. Digestion of the fragments with lipase liberated a rather typical cytochrome c in that it had absorption maxima in the reduced form at 550, 520, and 415 mμ, formed cyanide and pyridine hemochromogens which were spectroscopically similar to those obtained from mammalian cytochrome c, could be purified in the usual manner by ammonium sulfate fractionation, and had an oxidation potential at pH 7.0 of 0.25 v. As isolated, however, the cytochrome c was readily oxidized by oxygen in the air.