During the past ten years, approximately 3000 cases of knee arthroscopy have been performed in a CO2 medium. The setup for the use of CO2 is quite simple and is explained here on a step-by-step basis. Advantages are a better visual field and no motion of tissue in the arthroscopic field. The disadvantages are minimal. For these reasons, it is believed that CO2 arthroscopy is a significant adjunct to arthroscopy in a fluid medium.