This paper analyzes different aspects of the maximum-torque-per-ampere (MTPA) vector control of interior permanent-magnet synchronous motors at steady state and transient. Two different implementations are considered: a nonlinear-model-based MTPA profile including saturation and cross-saturation effects and a technique based on the maximization of the motor input power versus stator current. Furthermore, this paper analyzes the torque evolution during a transient under an MTPA control strategy on motors with different characteristics. Useful modifications of the current loop are suggested to improve the drive performance. The effects of the torque transient on the sensorless rotor position estimation are also taken into consideration, in case a sensorless MTPA implementation is required. Experimental results confirm the theoretical analysis, showing the benefits of the new control schemes.