The Social Science Data Archive (ADP) is a national resource centre, which acquires data from academic research projects and government or commercial surveys. Data stored in the Archive must meet specific, suitable standards for secondary analysis. They are used not only for comparative analyses, but also for examining the reliability and validity of existing measurement tools in the design of new studies. Stored data is in computer-readable form to facilitate further study, statistical analysis, and presentation. Methodological descriptions, such as defining target populations, sample size and design, survey procedures and measurements, provide the basis for assessing the quality of the data for specific research purposes. By the end of 1998, the Archive had registered about 150 data sets and annotated about 25 per cent. Data catalogued in the first round covers the following domains: Family, Ecology, Public opinion, Quality of life, Media, International relations, Migration, Politics and government, Religion, Social structure, Victimisation, Elections, Values. The Archives Study description catalogue is accessible on the internet.