Studies have been made on ATPase from chloroplasts, cyanobacteria and mitochondria of higher plants and animals. No intraspecies and interspecies variability of chloroplast and mitochondrial ATPase was found with respect to pH optimum of the activity, to specificity to cations as substrate components, to sensitivity to stimulating and inhibiting anions and ethanol, to optimal stimulating ethanol concentration. Intergenus variation of these properties of ATPase from chloroplasts, plant mitochondria, and cyanobacteria was revealed. Analysis of homology of the amino acid sequence in ATP-synthase subunits showed that ATP-synthase genes in chloroplast DNA originate from cyanobacterial genome, whereas ATP-synthase genes in plant and animal mitochondria-from genome of Rhodospirillum rubrum or closely related species. It was established that no recombination between the genetic material of chloroplasts and mitochondria took place during evolution.