Due to the increasingly stricter emission legislation and growing demands for lower fuel consumption, there have been significant efforts to improve combustion efficiency while satisfying the emission requirements. Homogeneous Charge Compression Ignition (HCCI) combined with turbo/supercharging on gasoline engines provides a particularly promising and, at the same time, a challenging approach.Naturally aspirated (n.a.) HCCI has already shown a considerable potential of about 14% in the New European Driving Cycle (NEDC) compared with a conventional 4-cylinder 2.0 liter gasoline Port Fuel Injection (PFI) engine without any advanced valve-train technology. The HCCI n.a. operation range is air breathing limited due to the hot residuals required for the self-ignition and to slow down reaction kinetics, and therefore is limited to a part-load operation area.Considering the future gasoline engine market with growing potentials identified on downsized gasoline engines, it becomes necessary to thoroughly investigate the synergies and challenges of boosted HCCI. Additional HCCI potentials can be realized through the additional breathing, resulting in extension of the operation map and further optimization of fuel efficiency. This provides additional potentials regarding test cycle efficiency. These potentials will be addressed in this work by thermodynamic analysis, drive-cycle simulations and split of losses. These analysis and simulations are based on single-cylinder and 4-cylinder engine data. As an outlook the new challenges associated with the boosted HCCI will also be discussed.