SUMMARYData are presented from a balanced backcross experiment involving three linkage group VI markers in the house mouse. These establish the order N–Ca–bt (naked–caracul–belted), and confirm the unusual recombination values reported earlier; the values for male heterozygotes are about 4 times those for the female ones. The linkage group is extended by the linkage of miniature, mn, with N and Ca, here reported. Data are given which establish the order mn–N–Ca–bt; they indicate that the recombination values for males may be greater than those for females for some way to the left of the N–Ca–bt segment.