Florida largemouth bass (Micropterus salmoides floridanus) have been stocked extensively into Texas reservoirs containing the northern largemouth bass (M. s. salmoides) subspecies, and knowledge of the genetic make-up of these potentially intergraded populations is important to their continued management. Bass populations from 19 such reservoirs were analyzed by electrophoretic determination of individual fish genotypes. As measured by variation at 3 loci, intergradation ranged from 2% to 92%. Variations in percent intergradation among reservoirs were related to individual reservoir conditions and Florida largemouth bass stocking histories. Regression analysis suggested that repeated annual stocking of Florida largemouth bass had the greatest effect on the frequency of Florida largemouth bass genes. Water clarity and total number of Florida largemouth bass stocked were correlated with intergradation rate, but did not explain significant additional variation beyond that due to number of years stocked.