perm is a permutation program designed to detect statistical connections between grouping structures and grouping factors or correlates. Groups may be of various kinds such as herds, flocks, schools and mating couples provided they make up meaningful social units. Relatedness, population membership and genotypic contents are among several aggregating variables which may be processed. Typically, perm takes in a collection of grouped data and outputs a P value. The latter is computed on the basis of random membership among groups (HO). All files, including input, output and program, are of Excel type (.xls). perm can be downloaded free of charge at: http://www.bio.ulaval.ca/louisbernatchez/downloads.htm.