Electrophoretic and activity variants for a testosterone-induced esteroprotease have been discovered in submaxillary glands from inbred strains of mice. The enzyme is tentatively designated tamase [TAM-1] and the variant genetic locus is Tam-1. The alleles Tam-1a and Tam-1b determine electrophoretically distinct zones of tamase activity, while Tam-lc produces no detectable enzyme activity. Data from recombinant inbred strains and B6AF1 X B6 and B6D2F1 X B6 backcrosses established linkage of Tam-1 to glucose phosphate isomerase (Gpi-1), pink-eyed dilution [p] and beta-hemoglobin (Hbb) on chromosome 7. The gene order is Gpi-1--Tam-1--p--HBB. Analysis of congenic resistant strains indicates that Tam-1 is closely linked to the minor histocompatibility locus, H-4. TAM-1 was not cross-reactive with antisera to mouse nerve growth factor, submaxillary renin, or tamases A and D.