Genetic maps of chromosomes 2 and 4 constructed from pair-wise lod score data from family studies and regional assignments for markers are presented. Two loci are mapped on chromosome 2 and multiple crossing-over is suggested as an explanation for the poor fit to the data in females. The best map of chromosome 4 gives the genetic locations of five markers with the Stoltzfus (SF) blood group distal to MNS on the long arm and GC close to the centromere on the short arm. This position for GC is outside its provisional regional assignment and possible reasons for this discrepancy are discussed. The GM-PI linkage group has a score of less than -1.0 with chromosome 4 suggesting that it may be excluded from that chromosome. The regional assignment for markers on chromosome 2-5 are also shown.