SUMMARY
Geographical Information Systems (GIS) have been used widely in zoology and ecology, particularly in herpetology. The use of spatially explicit analysis has increased during the last decade, with the consequent expansion of GIS application in ecology. During the last years, geo-information technology has been developed within the Free/Open Source Software (FOSS) community, resulting in new open source formats and several GIS packages. However, proprietary packages seem still to be the first choice for herpetologists, thus involving non negligible costs for GIS technology adoption. Additional costs arise from environmental data, which are usually expensive, worsening in the case of large study areas. An alternative solution is to use freely available data, despite a possible decrease of resolution. In this review, we aim to show the feasibility of spatial analysis within FOSS GIS packages, rank these packages using the number of available tools and list several data sources freely available on the Internet. We listed several websites providing the most important free data for spatial analysis, i.e. altitude and derived data; past, current and future climatic series data; and satellite derived data. We provide also a list of the most commonly used functions in GIS analysis and their availability in the six software compared in this study (ArcGIS; gvSIG; ILWIS; Quantum GIS; GRASS; and DIVA-GIS). The software gvSIG is the one with more functions (106) followed by Quantum GIS with 94 and GRASS with 84.