Mitochondria are organelles present in all eukaryotic organisms. Their primary function is production of energy in the form of ATP by oxidative phosphorylation. The final step of this process is catalyzed by an enzyme of internal mitochondrial membrane - ATP synthase. The ATP synthase consists of the seventeen subunits in yeast (in vertebrate sixteen is identified to date) organized in hydrophobic, membrane localized unit, referred to as F0 and hydrophilic domain F1 directed into mitochondria matrix. Genes encoding the ATP synthase subunits are mainly nuclear, but few of them, encoding hydrophobic subunits, are retained in mitochondrial genome in most Eukaryotes. Biogenesis of the ATP synthase is a sophisticated process, depending on the activity of proteins, which are not ATP synthase subunits, coordinating expression of the nuclear and mitochondrial genes and their assembly in active complex. This review summarizes the present knowledge about structure, biogenesis and mechanism of ATP synthase complex function.