A technique for bandwidth control of an electric discharge laser (2A). Line narrowing equipment is provided having at least one piezoelectric drive (14B1 - 14B5) and a fast bandwidth detection means and a bandwidth control having a time response of less than about 1.0 millisecond. In a preferred embodiment wavelength tuning mirrors (14C1 - 14C5) are dithered at dither rates of more than 500 dithers per second within a very narrow range of pivot angles to cause a dither in the wavelength values to produce a desired effective bandwidth of series of laser pulses.