The increasingly prominent role played by social science in society has helped to make much more information available on Portuguese society. Over the last decade the number of studies and publications on an increasing number of social facts has grown exponentially. However, much of the information produced, which is collected and entered into specific databases which have been put together for the purpose of specific research projects, never gets to see the light of day. A database has far too much potential to be discarded at the end of a research project following the publication of the projects studies and results. There is always a part of the information which is not comprehensively investigated and analyzed. At the same time, for analytical and economical reasons, the information is presented in an aggregated and reconstituted way, and not in the manner in which it is recorded and codified. In this way a significant proportion of scientific information remains statistically stored in computers. These limitations prevent researchers from taking full advantage of existing resources, and at the same time affect the control and critique functions of scientific activity. The solution which has been adopted in the international sphere has been the setting up of data banks. Organizations such as the ISPSR (Inter-university Consortium for Political and Social Research) in the USA, and the CESSDA (Council of European Social Science Data Archives) in Europe, have developed and encouraged the purchase, indexing and distribution of online electronic data for research and teaching in the social sciences. These organizations encourage the exchange of data and technology between similar organizations and co-operate in the development of organizations which have similar objectives. There are many advantages to setting up data banks. The ICPSR Guide to Social Science Data Preparation and Archiving outlines their main purposes: • To strengthen scientific research. • To encourage diversity of analysis and opinion. • To facilitate new research projects and to test new or alternative methods. • To improve data collection and measurement methods by examining those of others. • To reduce costs by avoiding duplication of data. • To provide a significant resource for training in research techniques and for teaching activities at the various different levels. Establishing a Social Science Data Archive allows for the development of two significant aspects of scientific activity. On the one hand, it encourages the development of secondary analysis of the data; and on the other, it reinforces the comparative aspect of academic studies. The development of secondary analysis of the data The sharing of data should be a regular part of scientific work. Many researchers want to make their data accessible to other researchers, but lack the resources to do so. The existence of a data bank makes it possible to disseminate much more widely the results of research and data collected, while at the same time making them communicable in operational terms. The availability of data for secondary analysis is not just useful for researchers interested in a particular issue. It may also turn out to be useful to all social science students who wish to develop a thesis or research project on the basis of the information which exists in the data archive. The possibility of taking advantage of information gathered as part of other projects in order to generate new knowledge on particular social facts is one of the most effective forms of achieving a satisfactory return on the investment in scientific activity. The development of comparative analysis in making information on Portuguese society openly available, a data archive encourages the comparative dimension of analysis. This dimension can be looked at from two angles: on the one hand, at the national level, it makes it possible to compare information gathered by different projects; and on the other hand, at the European level, it makes it possible to carry out comparisons between countries. Unlike other information processes for the dissemination of information, in particular through publication in print, a data archive gives the researcher freedom to build indicators and variables from the information he makes available, thereby providing a more consistent methodological foundation for the comparison. Such flexibility encourages the production of knowledge on a comparative basis. It is also likely that comparative analysis will encourage the exchange of information and lead to the development of collaborative efforts which will in turn strengthen the European element of scientific activity.