Abstract: A method and an apparatus for the treatment of either endo-cavital infections or abnormal surface tissue conditions, particularly destructive bacterial infections, post major invasive surgery abscesses and skin infections such as vitiligo and psoriasis. If required, a catheter system is used, which allows the simultaneous drainage of an infected locus and irradiation of the infected locus with laser-generated pulsed ultraviolet light. The laser light wavelength is chosen so as to require radiation, which is lethal to the microorganisms causing the infection, at the lowest possible dose which will provide ameliorative therapyty. Alternatively, a diode-pumped solid state Raman laser device is used which can be configured to provide in sequence a selected number of output wavelengths in the ultraviolet spectral range.