Available techniques for monitoring the health situation have proven insufficient, thus leading to a discussion of the need for their improvement based on new data collection strategies allowing for data use by local health systems. This article presents the methodological basis for a strategy to monitor health problems utilizing demarcated intra-urban spaces called "sentinel areas" to collect fundamental social, economic, behavioral, and biological data for public health that allow for a closer approach to the reality of complex social spaces. The authors present an experience that is being developed in Salvador, Bahia, Brazil, to evaluate the epidemiological impact of an environmental sanitation program. They discuss selection criteria for the areas and the potential uses of this strategy allowing for the rapid utilization of epidemiological resources by health services and the timely application of the results to reorient and enhance health intervention practices.