The decay rate of K-S --> gamma gamma has been measured with the NA48 detec
tor at the CERN SPS. A total of 149 K-S --> gamma gamma events have been ob
served. The branching ratio is determined to be (2.58 +/- 0.36(stat) +/- 0.
22(sys)) x 10(-6). (C) 2000 Elsevier Science B.V. All rights reserved.