Single contrast knee arthrography was performed in a group of 50 patients, using either Urografin or Ioexol as contrast agents. Both contrast media were well tolerated clinically and no significant difference was found to exist as far as image quality is concerned. However, while Urografin produced a significant increase of the white cells in the synovial fluid, no inflammatory change was observed in the synovial fluid after Ioexol. So we believe that Ioexol is a significantly preferable contrast medium in arthrography, especially in patients with inflammatory joint diseases.