GenAlEx, short for Genetic Analysis in Excel, is a user-friendly cross-platform package for population genetic analysis. Functions include AMOVA (see also Arlequin), spatial autocorrelation (see also SPAGeDI), Mantel tests (see also Permute! and TFPGA), and principle component analysis of genetic data. It runs within Microsoft Excel and so is not operating system specific. GenAlEx enables population genetic data analysis of codominant, haploid and binary genetic data providing analysis tools applicable to plants and animals. GenAlEx was originally developed as a tool to assist in teaching of population genetic analysis, and is now widely used by university teachers and researchers around the world.