Protein bodies (PBs) were isolated from germinating seeds of Lupinus angustifolius L. (cv. New Zealand Bitter Blue) by centrifugation in an isotonic medium. A membrane vesicle fraction was isolated from the organelle after solubilization of the protein matrix and found to have an associated NADH cytochrome c reductase. The reductase had a broad alkaline pH optimum and NADH was the favoured electron donor (Km=11.0 μM) whilst ferricyanide, dichlorophenol indophenol and cytochrome c were effective as electron acceptors. Cations were found to enhance (NH4+, Li+, Na+, K+, Rb+, Cs+, Mg2+) or decrease (Ca2+, Sr2+) the activity. Inhibitor studies enabled the partial characterization of the PB membrane NADH cytochrome c reductase and suggested that it was of a microsomal rather than mitochondrial type.