Development of laser sources in the 200-400 nm region made little progress before 1975. This spectral region claimed only low power, low efficiency ion lasers, a few metal vapor cw lasers such as Cd, and the pulsed N2 laser at 337.1 nm. This latter laser had been the workhorse for dye laser pumping and other uv applications. It has been supplanted now by the rapid and remarkable development of rare-gas halide excimer lasers. These excimer lasers, using several rare gas-halogen mixtures, span the 200-400 nm spectrum with at least six major, lines. The gas mixtures have lent themselves well to electron beam, discharge sustained, and pure discharge pumping techniques. They can be made to emit up to 500 MW of peak power in pulses from < 100 ns to nearly 1 μsec and with 5-10% efficiency. These lasers appear to be scalable to become large energy devices. Concurrent with such a scale-up, however, must come more knowledge about such problems as the formation pathways, excited state and ground state kinetics, halogen donor replenishment, and damage problems with mirrors and other optical components at these short wavelengths. These new lasers have made a great impact in the 200-400 nm region. They are the lasers of choice for: up-conversion to shorter wavelengths to access the VUV; down-conversion to generate blue-green wavelengths; for pumping of dye lasers; and for photochemistry where good sources of photons have been in great demand.