Steam autoclaving and ethylene gas sterilization method have been used for arthroscopes,but recently cold sterilization method using 2% glutaraldehyde solution was recommended.Although this method is economic, quick and excellent method, there has been a growing awareness of the minor complication associated with arthroscopy, particulsrily effusion and wound healing. So, we attemped to evaluate the effect of activated glutaraldehyde solution in knee arthroscopy. We have done so as follows : 1. Observed the intra-articular response (grossly, light and electron microscopically) of rabbit knees, three weeks after a single injection of glutaraldehyde at concentration of 0 to 1000 ppm. 2. Measured the glutaraldehyde concentration in the rinse solution using a sensitive spectrophotometric technique. 3. Measured the glutaraldehyde concentration in the intraoperative joint irrigation solution as same as above technique. The results were as follows : 1. Grossly, diffuse synovitis was observed with dose of 100 ppm or greater, and the degree of inflammation was proportional to the glutaraldehyde concentration. We have observed microscopic evidence of a few leukocyte infiltration and vascular congestion in the synovium of rabbit knees, injected with 5 ppm glutaraldehyde. At concentration of 50ppm, vascular hemorrhage and synovial edema, at 500ppm, focal synovial necrosis and fibrosis were observed. At 1000ppm, chondrolysis was observed. Electron microscopically we have observed synovial cells proliferation, especially type B cells and interstitial edematous changes, injected with 5-10 ppm glutaraldehyde. At concentration 50 ppm, synovial cells are decreased in number and marked vacuolization changes, at 100 ppm, synovial cells are denuded on the surface. 2. The concentration of glutaraldehyde present in the rinse basin was 16–30 ppm by thefirst rinsing procedure, if the same rinse solution was used for subsequent cases, the lutaraldehyde concentration was 117–149 ppm by the sixth rinsing procedure. 3. The concentration of glutaraldehyde present in the intraoperative joint irrigation solution was less than 1 ppm.