In a method and an apparatus for operating an injection system of an internal combustion engine, triggering of an injection actuator being performed on the basis of at least one state variable of the injection system, in order to enhance the quantitative accuracy with which fuel is metered provision is made that the at least one state variable is sensed and temporarily stored; the at least one injection actuator is triggered with a triggering pulse of definable pulse duration and definable initial pulse height; during the triggering of the at least one injection actuator, an injection detection is performed; the pulse height of the triggering pulse is incremented in definable steps, at the defined pulse duration, until an injection is detected; and when an injection is detected, the pulse height of the triggering pulse causing the injection is permanently stored as a function of the sensed state variable, and in future operation of the injection system is taken as the basis for triggering the at least one injection actuator.