In each of 3 successive generations of selection, ♂ and ♀ C57BL/6J mice showing preference for the same paw (left or right) were mated together, as were mice showing preference for different paws. Irrespective of the type of mating or the stage of selection, roughly one half of the offspring were dextral and one half sinistral. These results suggest that paw preference variation in mice is neither maintained by a residue of heritable genetic variation nor influenced significantly by transmissible cultural factors associated with the parental phenotypes. No sex differences was observed in lateral preference. Of 858 C57BL/ 6J mice tested, 52.7% exhibited left paw preference. The slight excess of sinistral mice was not statistically significant. [For Pt. I see A.B.A. 37, No. 1767.