An R package for the statistical analysis of ChIP-seq experiments. CSAR calculates single-nucleotide read-enrichment values, taking the average size of DNA fragments subjected to sequencing into account. After normalization, sample and control are compared using a test based on the ratio test or the Poisson distribution. Test statistic thresholds to control the false discovery rate are obtained through random permutations. Computational efficiency is achieved by implementing the most time-consuming functions in C++ and integrating these in the R package.