The elaboration of land use and land cover thematic maps, based on satellite remote sensing data, for the monitoring of natural resources, has been quite common in Brazilian governmental institutions related to the environment, agriculture, geography and statistics areas. Most of the time these mappings are performed on a large territorial scale, covering entire biomes or several aggregate states, which makes difficult to carry out field work to assess the accuracy of the mapping done. Specific applications that use the Web-GIS concept have been developed and successfully employed for validation tasks, aiming to associate an accuracy value with the mapping information. This paper demonstrates the development and practical implementation of an application to validate land use mapping data in the Brazilian Cerrado (TerraClass Cerrado), which can be easily adapted to other biomes.