ENMTools interacts with the maximum entropy niche modeling program Maxent (Phillips et al. 2006, Phillips and Dudík 2008), allowing users to automate generation of ENMs, calculate similarity measures, and implement various statistical comparisons of ENMs. Although ENMTools is designed to interact directly only with Maxent, the pseudoreplicate data sets that it generates for hypothesis testing can be used with other methods of ENM construction. ENMTools is a Perl script with a graphical user interface written with the Tk package. It is also available as an executable file for Windows and Macintosh. In theory, the ENMTools Perl script may be implemented on any platform capable of running Perl and the associated Tkx package with minor adjustments. In practice, ENMTools has been implemented only on the Microsoft Windows and Mac OS X platforms. ENMTools requires working installations of Maxent and Java. Input for ENMTools is similar to that required by the widely used Maxent niche modeling software and consists of simple .asc and .csv-formatted text files containing locality data for two or more populations and associated ASCII-formatted GIS raster layers of environmental data.