In spite of the many improvements in arthroscopic surgical techniques for the treatment of mild to moderate degree degenerative joint diseases which were resistant to conservative treatment, the results are variable, showing a tendency to decline in therapeutically following the passage of time. Using a 2.1 un holmium: YAG laser we operated on patients with mild to moderate degenerative joint diseases which had not improved through conservative treatment. We evaluated the results of arthroscopic laser surgery for degenerative joint disease and investigated the proper indication and complications of laser surgery. We operated on 28 knees of 28 patients between July 1995 and June 1996. There were 16 females and 12 males. The average follow-up period was 16.3 months and the average age was 54.5 years. Under epidural or general anesthesia, we used arthroscopic tools, including laser, and the laser power was modified according to the type of operation (chondroplasty: 1.0J×20pulse/sec, meniscectomy: 2.0J×15pulse/sec, bone drilling: 2.5J×10 pulse/sec). We used Bauer & Jackson's classification of articular cartilage change, and performed 12 laser chondroplasties in grade II, III, V lesions, 16 chondroplasties and laser bone drilling in grade IV, VI lesions, 16 laser meniscectomies, 6 laser synovectomies and 2 lateral retinacular releases. Medial femorotibial arthritis was the most common site. Postoperative results by Orgilvis-Harris & Fitsialos's methods indicated that 82% of treated patients were satisfied and only two patients (7%) did not improve. As a postoperative complication, eight patients complained of postoperative effusion which was subsided by medication and physical therapy. We performed second-look arthroscopic examinations in four knees that had been treated with laser chondroplasy and drilling. Regenerated tissues at the operated site were observed in three cases, but denuded articular cartilage and naked subchondral bone at the operated site were found in one case as a sign of osteonecrosis. Concluding this short-term study, 2.1 holmium: YAG laser in arthroscopic surgery seems to be effective in mild to moderate degenerative joint disease but care should be taken to avoid thermal injuries to the adjacent normal cartilages.