The SeSAM R package allows fully automatic construction of two successive genetic maps: a first one including an optimized subset of markers ensuring the robustness of orders to a given statistical threshold, and a second one including almost all polymorphic markers. It can handle all common types of biparental mapping populations, including progenies obtained from crossing heterozygous parents. In addition to the automatic procedure, SeSAM includes many functions for interactive mapping, file formats conversions, and generates many graphs useful to assess the quality of data and maps.