This TURBO PASCAL program DistoN yields pairwise estimates of diversity that can be used to measure Gst or Nst as a function of distance. These measures are based on haploid population genetic data, when the difference in number of repeats between alleles is available. The source file should be an ASCII file (its name should have 8 characters maximum: 12345678.txt) and should include the following information : First line : Number of cytotypes Number of populations Number of characters (loci, polymorphic fragments...). Then follows the number of individuals having a given haplotype (column) in a given population (row). Finally, and without interruption, provide the table of length variant states for all haplotypes, where each line corresponds to one haplotype, and each column to a character. No column should be empty (no missing haplotype) and each population (row) should be composed of AT LEAST 3 individuals! The output file provides the number of the two populations compared, followed by values of pairwise hs, ht, vs, vt in a single row. To see if Gst or Nst changes with distance, compute separetely the distance (in km for instance) between populations, and compute mean values of these four estimates for each distance class. Then derive Gst (or Nst) for that distance class as: 1-mean hs/ mean ht (or 1-mean vs/mean vt).