A standard, relatively old, large-frame argon-ion laser, which is available in many laboratories, was modified to produce output in the deep- UV (275-306 nm) region by installing a set of inexpensive, commercially available laser mirrors. The deep-UV output is generally applicable as excitation wavelength in the field of biochemical and environmental analysis. However, it has received little attention in the literature, probably because a complete laser set-up normally requires a high investment. The modification described, which includes a thorough cleaning of the Brewster windows of the laser tube and a careful alignment of the laser, is a good alternative to this investment. In daily operation, only some minor realignments are required. As an illustration of the applicability, excitation with the 275.4- nm line was used for laser-induced detection of native fluorescent aromatic sulphonates in capillary electrophoresis.