This chapter is devoted to gear pairs formed by two identical circular involute gears mounted eccentrically on their shafts. The issues of kinematics and dynamics of such gear drives are considered. The method of designing EM gears is proposed, including the choice of eccentricity, dimensioning of gears and determination of module and number of teeth depending on the load, rotational speed, and strength of the material the gear rim is made of. The text is accompanied by design formulas and diagrams that make the design process relatively easy and quick. An example of design and calculations contributes to the better understanding of the proposed method.