A side-firing fiber device for arthroscopic Ho:YAG (λ=2.12 μm) and Er:YAG (λ=2.94 μm) laser applications was designed and constructed. The fiber delivery instrument consisted of a zirconium fluoride (ZrF4) fiber equipped with a coaxially mounted short end-piece of low OH quartz fiber polished at an angle of 30 deg. The dynamics and depth of the vapor channel in water and the amplitude of pressure transients associated with the collapse of the vapor channel were measured for pulse energies up to 1 J (Ho:YAG) and 200 mJ for the Er:YAG laser (pulse duration τ=400 μs), respectively. To assess the feasibility of the side-firing fiber delivery instrument, the ablation efficiency and laser-induced damage in poly(acylamide) and meniscal tissue were determined after Ho:YAG and Er:YAG laser ablation. © 1998 Society of Photo-Optical Instrumentation Engineers.