The Pan American Health Organization (PAHO) Core Data project is a response for monitoring major PAHO/WHO health initiatives and mandates in the Americas that provides users with a minimum set of standardized health-related data and country profile documents. The project promotes the use of basic health information for decision making in the health sector. Data will facilitate the characterization of the health situation in 48 countries or define the situation and importance of priority problems and conditions. A total of 118 of accepted demographic, social, economic, and mortality and morbidity risk factors and resources, access, and coverage of health services indicators have been included in the database, the majority of them by age and sex. A three-tier Web-based GIS with a basic and an advanced user interface has been developed to allow users to retrieve, display, and analyze health-related data. The architecture of the system includes, on the server side, a relational database management system (RDBMS-SQL server), a GIS with Web-based extensions, and a Web server, and on the client side, applets and scripts for graphical user interface (GUI) and HTML tags through a Web browser. The GUI allows online queries from the Web client side. The basic output in HTML format includes tables with countries by indicator (definition and sources of data are linked to each indicator), thematic maps of each indicator by subregions, and bar charts for country by indicator. Each of them allows linking to other documents such as country profiles that provide a reference framework. An advanced Java-based system has additional capabilities including zooming, panning, selection of critical areas, and other types of thematic mapping. While originally designed for the Intranet, the system will be available for Internet users in the near future on the PAHO Web site (http://www.paho.org).