Abstract: A wave generator has a circular spline, a flexspline inside the circular spline and a plug inside the flex spline. The plug is asymmetrical and is preferably formed to comprise a semi-elliptical first portion and a semi-cylindrical second portion. The diameter of the semi-cylindrical portion coincides with the major axis of the semi-elliptical portion. Gear teeth on the circular spline and on the flex spline are meshed in only a first zone and unmeshed in a second zone. The flexspline in the harmonic drive gear assembly according to the present invention preferably has only one tooth fewer than the circular spline so that the circular spline rotates through and arc defined by one gear tooth for each complete revolution of the flexspline.