A lipid-depleted QH₂-cytochrome c reductase has been prepared by a column of calcium phosphate.The activity of this enzyme is lower and the cytochromes contained in this enzyme is partially (about 53 % of cytochrome b and 83 % of cytochrome c₁) reduced. The reconstitution of the lipid-depleted QH₂-cytochrome c reductase with lipids can not only recover the activity but also induce the reduced cytochromes retain to its oxidized state. This result indicates that a special interaction between the lipid and protein is important for keeping the enzyme in its native conformation.