Ames dwarf (df) is an autosomal recessive mutation characterized by severe dwarfism and infertility. This mutation provides a mouse model for panhypopituitarism. The dwarf phenotype results from failure in the differentiation of the cells which produce growth hormone, prolactin, and thyroid stimulating hormone. Using the backcross (DF/B-df/df X CASA/Rk) X DF/B-df/df, we confirmed the assignment of df to mouse chromosome 11 and demonstrated recombination between df and the growth hormone gene. This backcross is an invaluable resource for screening candidate genes for the df mutation. The df locus maps to less than 1 cM distal to Pad-1 (0.85 +/- 0.85 cM). Two new genes localized on mouse chromosome 11, Rpo2-1, and Edp-1, map to a region of conserved synteny with human chromosome 17. The localization of the alpha 1 adrenergic receptor, Adra-1, extends a known region of synteny conservation between mouse chromosome 11 and human chromosome 5, and suggests that a human counterpart to df would map to human chromosome 5.