This test measures chromosome events in spermatogonial germ cells and is, therefore, expected to be predictive of induction of inheritable mutations in germ cells.

Male Chinese hamsters and mice are commonly used. Animals are exposed to the test substance (liquid or solid) by an appropriate route of exposure, usually by gavage or by intraperitoneal injection. Then, they are sacrificed at appropriate times after treatment. Each treated and control group must include at least five analysable males. Test substances are preferably administered once or twice but they may also be administered as a split dose to facilitate administering a large volume of material. Prior to sacrifice, animals are treated with a metaphase-arresting agent. Chromosome preparations are then made from germ cells and stained, and metaphase cells are analyzed for chromosome aberrations. A limit test may be performed if no effects would be expected at a dose of 2000 mg/kg bw/d. Positive results from the in vivo spermatogonial chromosome aberration test indicate that a substance induces chromosome aberrations in the germ cells of the species tested.