This study is part of a larger effort working toward the development of mammalian in situ genetic biomonitors. It examines the frequency of structural chromosome aberrations in standard bone marrow metaphase preparations of three rodent species inhabiting a site contaminated with Aroclor 1254. These data are compared to those of conspecifics from uncontaminated reference areas. In the case of 2 species, comparisons are also made to conspecifics from an area contaminated with substances associated with the induction of structural chromosome aberrations and significant variation in whole cell DNA content.Zoolog