an apparatus for operating a gaseous discharge lamp comprises a d . c . power source , a transistor inverter which is connected to the d . c . power source through a switch , provided with at least one inverter transistor and generates an output having a prescribed frequency , and a discharge lamp which is energized by an output from the transistor inverter and having a pair of electrodes heated by part of the output . the apparatus further comprises base current control means which holds the base current of the inverter transistor at a level lower than a first level during a prescribed length of time after the close of the switch , and holds the base current at the first level after the prescribed length of time . the discharge lamp has its electrodes preheated , but does not display discharge when the base current has a level lower than the first level , and commences discharge when the base current reaches the first level and thereafter continues discharge .