The potential of a new continuous wave Thulium YAG laser is investigated for tissue ablation and cutting focusing on applications in minimally invasive surgery. The laser emits at a wavelength of 2.01μm, which is well suited for tissue ablation due to its high absorption by water. The laser power can be tuned up to 60 W output through a 365 μm core diameter quartz fibre. For the ablation studies, the quartz fibre was placed in contact under various pressures (20 to 90mN) to porcine liver under saline solution in vitro at angles varying between 30° to 60°. The influence of different powers (10 to 60W) and cutting velocities (2 to 10mm/s) on the incision depth and coagulation zones of the tissue were investigated. A maximum incision depth of 3.3 mm was found with a power of 60W, a cutting velocity of 2mm/s and a fibre-tissue angle of 45°. The incisions were surrounded by coagulated tissue between 0.4 and 0.8mm in thickness, sometimes with an inner zone of carbonization of 0.2mm on average. In conclusion, the first experiments show that a cw Thulium laser is very well suited for tissue dissection as required in minimally invasive surgery.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.