AbstractStrain DBA/2J male mice were treated with triethylenemelamine (TEM) and subsequently mated to strain C57BL/6J females. Tissues from F1progeny produced in these crosses were then examined using starch gel electrophoresis for the presence of presumed induced mutations at a series of 11 specific enzyme loci. In the course of this study, four heritable mutations were identified at the following loci:Es‐1, Ldh‐1, Pgm‐1, andGpi‐1. Of these four, the first two were apparently segregating in parental males and were not TEM‐induced. Both of these are viable and fertile in the heterozygous and homozygous condition, and neither confers any readily apparent deleterious effect to the animal. The latter mutations(Pgm‐1andGpi‐1)are presumably induced. Although viable and fertile in the heterozygous state, we have not yet recovered any offspring homozygous for either of these