This report sought to critically examine proposals, potentials, and challenges of environmental health observatories with an emphasis on climate change processes. A critical review of existing environmental health observatories was performed, examining their purposes, potential audiences, and technological platforms. The implementation of the Brazilian Climate and Health Observatory (C&HO) is described, and two stages are defined: (i) the requirement analysis and negotiation stage that identified the national and regional institutional players and their roles as data producers/users; and (ii) thematic health-related workshops that reviewed water-related diseases, vector-borne diseases, extreme climate events, and health problems derived from forest fires. The C&HO is an example of making information on climate and health available through an Internet site where data from different origins can be accessed on a common platform. Complex queries are made by users and can be executed over multiple sites, geographically distributed, with all technical details hidden from the end user. At this stage of the C&HO prototype, alongside the queries, users can also produce semi-qualitative graphs and maps. A multi-scale approach was developed using the platform by setting up sentinel sites. Building a successful observatory is a participatory process that involves choosing indicators, data sources, information technology, and languages to best reach different audiences, such as researchers, citizens, public health professionals, and decisionmakers.