Florida largemouth bass (Micropterus salmoides floridanus) have been intensively stocked throughout the southern United States for the past three to four decades due to perceived superior growth characteristics. As a result, introgression of Florida largemouth bass with native stocks of northern largemouth bass (M. s. salmoides) has been prevalent. Lakes Ashbaugh and SWEPCO, located in northern Arkansas, were both constructed near 1980 and initially stocked with Florida largemouth bass (LMB). Allele frequencies of three discriminant allozyme loci (sAAT-B, sIDH-B, sMDH-B) between Florida and northern largemouth bass were determined for LMB collected between 1994–1996. Florida largemouth bass alleles were common within each reservoir, yet more common in SWEPCO Lake, a cooling pond for a coal powered electric plant. FLMB allele frequencies in Lake Ashbaugh bass were 0.20 for sAAT-B*3–4 alleles, to 0.24 for sIDHP-B*2 and 0.27 for sMDH-B*2; SWEPCO Lake FLMB allele frequencies were highly variable, with 0.58 for sIDHP-B*2 alleles, 0.64 for sAAT-B*3–4 and 0.92 for sMDH-B*2. High incidence of Hardy- Weinberg disequilibrium was observed, indicative of genetic change within both populations. LMB alleles within the sMDH-B locus may be under selective pressure in SWEPCO Lake. Caution should prevail when introducing non- native stock into native gene complexes, as introduced genes persist through many generations.