Multiparent crosses of recombinant inbred lines provide opportunity to map markers and quantitative trait loci (QTL) with much greater resolution than is possible in biparental crosses. Realizing the full potential of these crosses requires computational tools capable of handling the increased statistical complexity of the analyses. R/mpMap provides a flexible and extensible environment, which interfaces easily with other packages to satisfy this demand. Functions in the package encompass simulation, marker map construction, haplotype reconstruction and QTL mapping. We demonstrate the easy-to-use features of mpMap through a simulated data example.