The cross-field theory as applied to single-phase induction motors is extended to develop a concise yet comprehensive theory for asymmetric three-phase induction motors. Each phase is represented by its equivalent circuit not only to allow for uneven direct transformer interactions due to asymmetric locactions of phase windings but also to account for the different number of turns, wire size, winding factor, etc., each phase may have. The accuracy of the theory was confirmed by actual measurements on symmetric and asymmetric three-phase induction motors. Computed and test data on some motors are included for illustration. It is also shown that the general three-phase development can be easily applied to determine the behavior of two- and single-phase induction machines-a useful feature for unified computer-aided design - by eliminating one and two phase windings respectively. Not only the procedural details for determining the performance of single-and two-phase induction motors are given but comparisons of numerical and test results on some output entities are included as well.