The optimum performance of a regenerative Brayton cycle was analyzed. The model includes external and internal irreversibilities coming from four main sources: coupling to external heat reservoirs, turbine and compressor nonisentropic processes, pressure losses in the heater and the cooler, and the regenerator. In terms of the parameters accounting for each type of irreversibility, explicit numerical results are presented for the maximum efficiency, maximum power output, efficiency at maximum power output, power output at maximum efficiency, as well as for the pressure ratios required for maximum efficiency and maximum power. This analysis could provide a general theoretical tool for the optimal design and operation of real regenerative gas turbine power plants. ©1997 American Institute of Physics.