The R-package postHoc implements a range of facilities for post-hoc analysis and summarizing for linear models, generalized linear models and generalized linear mixed models, including grouping and clustering via pairwise comparisons using graph representations and efficient algorithms for finding maximal cliques of a graph. It has S3 methods for printing summarizing, and producing plots, line and barplots suitable for post-hoc analyses. The package is available at the CRAN.