Abstract: A pulse width luminance modulation system for driving a gas discharge panel in line at a time. The driving circuit for the discharge cell comprises a CR time constant element in order to enlarge the contrast range of the picture to be displayed. The discharge cell is caused to produce glow discharge when the pulse width of the pulse width modulation driving pulse is wider than a certain value depending on the CR time constant to produce normal pulse width luminance modulation of the glow discharge, and the discharge cell is caused to produce instantaneous irradiation of which the intensity is dependent on a stored charge in the capacitive element C of the CR element when the driving pulse width is narrower than the certain value so as to widen the low luminance range and by suitably selecting the value of the CR element for obtaining continuity of the two luminance characteristics, and further the input signal for making luminance modulation is applied with a correction in order to make the .gamma.