The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has the primary competency for managing fishing south of the Antarctic Polar Front. Despite a relatively long history of scientific research and fisheries, CCAMLR’s fisheries management strategy has often had to address incomplete and uncertain information on affected resources. Fishery-independent studies are difficult and expensive to conduct. In addition, the size of the Convention Area, its remoteness and prevailing inclement weather have complicated matters. Therefore, in addition to the standard catch and effort data supplied by vessels, the collection of data by scientifically qualified observers aboard fishing vessels has assumed prominence in the collection of essential data for fisheries management purposes. The Scheme of International Scientific Observation, adopted by CCAMLR in 1992, is designed to gather and validate fishery-related information essential for assessing target species status as well as the impact of fishing on dependent and related species, including seabirds and marine mammals. The Scheme is limited to scientific observation only and is carefully separated from enforcement aspects falling covered by the CCAMLR System of Inspection. Under the Scheme observers are deployed under bilateral agreements between CCAMLR Members and they operate on vessels under flags other than their own country. This paper outlines the Scheme's history in terms of its logistics, participation and coverage, changes in research priorities, volume of data collected and data usage. The Scheme’s benefits and shortcomings are explored and an attempt is made to evaluate the total annual cost of scientific observer programs.