The ESO Science Archive Catalog contains a log of observations performed with the ESO telescopes. Currently available in the observation log are the data from the VLT, NTT, MPG/ESO 2.2m, and the ESO 3.6m telescopes. The observations themselves are stored in an off-line archive and have a proprietary period of one year. After this period the archival data sets are available to the general astronomical community of the ESO member states and Chile.