Abstract: The structure of the dimeric ATP synthase from yeast mitochondria was analyzed by transmission electron microscopy and single particle image analysis. In addition to the previously reported side views of the dimer, top view and intermediate projections served to resolve the arrangement of the rotary c10 ring and the other stator subunits at the Fo-Fo dimeric interface. A three-dimensional reconstruction of the complex was calculated from a data set of 9,960 molecular images at a resolution of 27 Angstroms. The structural model of the dimeric ATP synthase shows the two monomers arranged at an angle of ~45 degrees, consistent with our earlier analysis of the ATP synthase from bovine heart mitochondria (Minauro-Sanmiguel, F., Wilkens, S. and Garcia, J.J. (2005) Proc. Natl. Acad. Sci. USA 102, 12356-8). In the ATP synthase dimer, the two peripheral stalks are located near the F1-F1 interface but turned away from each other so that they are not in contact. Based on the three-dimensional reconstruction, a model of how dimeric ATP synthase assembles to form the higher order oligomeric structures that are required for mitochondrial cristae biogenesis is discussed.