A method for resonant switching applicable to dc to dc power conversion is presented. Zero current switching together with resonant control of current waveforms avoids solid state power device second breakdown stresses encountered with high voltage switching in conventional circuitry. General theory of circuit operation and design is described. Circuitry and performance are outlined for an operational 1500 watt dc to dc converter designed for nominal input voltage of 270 Vdc, with regulated output voltage in the 90 Vdc range. Operational performance and projected power densities (watts per pound) are found to be attractively competitive with the existing state-of-the-art. Further development work is being done at Martin Marietta Aerospace using resonant switching frequencies in the 200 KHz range for space flight hardware. Projected power density in this application is 140 watts per pound, under high performance and reliability requirements.