This proposal focuses on the potential contribution of electromagnetic fields (EMF) to mutagenesis in conjunction with free-radical producing mutagens. These experiments are motivated by the recent chemical studies demonstrating the stabilization of free radicals by EMF. We propose to examine the potential mutagenic enhancing effects of EMF using the lacI transgenic rat embryo fibroblast cell line, R2lambdaLIZ. LacI mutant frequencies will be determined from untreated cells exposed to the mutagens adriamycin, nickel, or ethylnitrosourea (ENU) in the presence or absence of a 60 Hz magnetic field. In addition, mutational spectra for each exposure group will be ascertained by automated DNA sequencing of the lacI mutational target, to detect any sequence changes induced by the field and the concurrent mutagen exposures.