Results are reported of a comparative analysis of information obtained on total ozone content (TOC), using simultaneously recorded data from satellite (TOMS and SBUV instrumentation) and surface (Dobson spectrophotometer) observations of the city of Athens, Greece during the period 3 January to 31 December, 1991. The comparison revealed their satisfactory agreement when the satellite data are systematically understated to account for ozone in the cloud layer and in the atmosphere beneath the clouds. The need for an interactive system of satellite and surface observations of TOC, with the important role of the latter as a control, is emphasized.