Since the chemiosmotic theory was proposed by Peter Mitchell in the 1960s, a major objective has been to elucidate the mechanism of coupling of the transmembrane proton motive force, created by respiration or photosynthesis, to the synthesis of ATP from ADP and inorganic phosphate. Recently, significant progress has been made towards establishing the complete structure of ATP synthase and revealing its mechanism. The X-ray structure of the F(1) catalytic domain has been completed and an electron density map of the F(1)-c(10) subcomplex has provided a glimpse of the motor in the membrane domain. Direct microscopic observation of rotation has been extended to F(1)-ATPase and F(1)F(o)-ATPase complexes.