Sensitive, reproducible and cost-effective methods are needed to evaluate the potential of chemicals to induce DNA damage in male and especially, female germ cells. The Single Cell Gel (SCG) electrophoresis assay is a sensitive method for detecting single strand DNA breaks and alkali-labile sites in the DNA of individual cells. Using samples consisting of a few thousand cells, this assay can provide information on the intercellular distribution and persistence of DNA damage induced in mouse germ cells (spermatocytes and round spermatids) by chemical agents. The purpose of the proposed study is: (i) To further characterize the sensitivity and suitability of this technique for detecting different classes of germ cell DNA damage in male mice exposed to mutagens and nonmutagens. Blood leukocytes are used to provide information about somatic versus germ cell levels of damage: (ii) To determine if the technique can be used to detect DNA damage in ovarian cells from mutagen treated female mice: (iii) To extend the data base to a second species (e.g., rat). The availability of a technically simple male/female germ cell assay would greatly increase germ cell research by government agencies and the private sector.