Publisher Summary This chapter describes the procedures for purifying succinate dehydrogenase and complex IV from sweet potato root mitochondria, as well as properties of the purified enzymes. Complex IV that catalyzes has been purified from sweet potato root and pea shoot mitochondria. The purified sweet potato complex has a high specific activity, whereas the pea complex is inactivated during purification. The sweet potato complex, but not the pea one, can be solubilized with a high concentration of deoxycholate from submitochondrial particles, which have been washed with a low concentration of the detergent. Pea complex IV can be solubilized from the deoxycholate-washed submitochondrial particles only with high concentrations of Triton X-100; in such a case, the complex is very difficult to isolate in an active form. The subunit composition of sweet potato and pea complex IV has been analyzed by electrophoresis on polyacrylamide gels, containing sodium dodecyl Sulfate (SDS) and urea.