We present eight computer programs written in the C programming language that are designed to analyze genotypic data and to support existing software used to construct genetic linkage maps. Although each program has a unique purpose, they all share the common goals of affording a greater understanding of genetic linkage data and of automating tasks to make computers more effective tools for map building. The PIC/HET and FAMINFO programs automate calculation of relevant quantities such as heterozygosity, PIC, allele frequencies, and informativeness of markers and pedigrees. PREINPUT simplifies data submissions to the Centre d'Etude du Polymorphisme Humain (CEPH) data base by creating a file with genotype assignments that CEPH's INPUT program would otherwise require to be input manually. INHERIT is a program written specifically for mapping the X chromosome: by assigning a dummy allele to males, in the nonpseudoautosomal region, it eliminates falsely perceived noninheritances in the data set. The remaining four programs complement the previously published genetic linkage mapping software CRI-MAP and LINKAGE. TWOTABLE produces a more readable format for the output of CRI-MAP two-point calculations; UNMERGE is the converse to CRI-MAP's merge option; and GENLINK and LINKGEN automatically convert between the genotypic data file formats required by these packages. All eight applications read input from the same types of data files that are used by CRI-MAP and LINKAGE. Their use has simplified the management of data, has increased knowledge of the content of information in pedigrees, and has reduced the amount of time needed to construct genetic linkage maps of chromosomes.