Various types of electric machines can be considered for an application to integrated starter generator (ISG). Permanent magnet (PM) synchronous machines present interesting performances; nevertheless, it remains difficult to reach a significant constant power zone under good efficiency conditions and power factor. The loss of control of electronics at high-speed operations may lead to high-terminal voltages, which can become dangerous for the whole vehicle. In this study, we examine the main advantages and drawbacks of the induction machine, reluctant, and PM machine. Then we present more precisely the wound rotor synchronous machine (WRSM) performances for ISG applications. All these machines must follow strict rules and specifications (low length, high torque, speed, and efficiency). Different kinds of machines have already been evaluated.