The establishment of the International Monitoring System (IMS), which consists of a worldwide network of 321 seismic, hydroacoustic, infrasound and radionuclide stations and 16 radionuclide laboratories, continues to be developed steadily and securely. During 2002, 23 additional stations were certified as meeting the technical requirements of the Commission, bringing the total number of certified facilities at the end of 2002 to 47. Thus at the end of 2002, 46% of the stations in the IMS, including two Antarctic stations, were completed and met or substantially met the Commission’s specifications. Since the beginning of 2003, 3 additional stations have been certified, bringing the total to 50 certified facilities. The year 2002 was also the year in which the first large scale field experiment in on-site inspection (OSI) was conducted. More than 25 surrogate inspectors, from 17 States Signatories and the PTS staff, performed a simulation of inspection activities, including helicopter overflight, in a remote part of Kazakhstan.  ....