Electron transport activities in the turnip microsome fraction were char-acterized. Cytochrome c, 2,6-dichlorophenolindophenol (DCPIP), ferricyanide (FeCN), and neotetrazolium were reduced in the presence of NADH and NADPH, NADPH supporting a rate usually less than 10% that with NADH. Cytochrome ba was present and implicated in cytochrome c reduction. However, cytochrome P-450 was not detected.