SaTScan is a free software that analyzes spatial, temporal and space-time data using the spatial, temporal, or space-time scan statistics. It is designed for any of the following interrelated purposes: Perform geographical surveillance of disease, to detect spatial or space-time disease clusters, and to see if they are statistically significant. Test whether a disease is randomly distributed over space, over time or over space and time. Evaluate the statistical significance of disease cluster alarms. Perform repeated time-periodic disease surveillance for early detection of disease outbreaks. The software may also be used for similar problems in other fields such as archaeology, astronomy, botany, criminology, ecology, economics, engineering, forestry, genetics, geography, geology, history, neurology or zoology.