A ballast for starting and operating a high intensity discharge (HID) lamp in a dc mode includes an oscillator coupled to first and second direct current input terminals. The oscillator includes a high frequency generator driving a pair of semiconductor switches. A first transformer having primary and secondary windings is coupled to the semiconductor switches. A rectifier and voltage multiplier circuit converts the voltage across the secondary winding of the first transformer to a dc voltage. A first energy storage circuit coupled to the rectifier and voltage multiplier circuit stores energy for generating a negative-going, high-voltage spike sufficient for initiating a glow condition in the lamp. A second energy storage circuit, which stores energy for application to the HID lamp during starting, insures proper glow-to-arc transition. The starting and operating circuit further includes a control circuit for regulating lamp power in response to control signals received from voltage and current monitoring circuits. A portion of the ballast is adapted to permit the lamp to reach full light output in a relatively short period of time by briefly operating the lamp at an elevated power level during starting.