New high-efficiency ultraviolet and vacuum ultraviolet excimer lamps pumped by microwavedischarge are reviewed. KrF (B→X) and ArF (B→X) fluorescences of a 9-ms pulse durationwith a 100-Hz operation frequency and of 6-μs pulse duration with a 100-kHz operation fre-quency were observed. The spectral widths were around 3nm as narrow as those of excimerlasers. The highest intrinsic efficiency of 12.5% was obtained with a high average KrF power of 43W. Theoretical analysis of a pulsed KrF excimer lamp is also described.