New electrophoretic analyses have provided additional information concerning intraspecific genetic variation among largemouth bass Micropterus salmoides. Genetic differences, previously unknown, were found among four stocks of largemouth bass, two of them domestic and two of which were one generation removed from the wild. The domestic stocks were derived from intergrade populations of northern and Florida subspecies; one nonintergrade stock represented the northern subspecies M. s. salmoides and the other represented the Florida subspecies M. s. floridanus. More than 60 presumptive loci were electrophoretically examined. At least 11 loci were polymorphic. Of the polymorphic loci, two represented previously known fixed subspecific differences and two or perhaps three represented previously known allele frequency differences. Variation among the stocks at the remaining loci was expressed as allele frequency differences. Allelic polymorphisms restricted in our sample to Florida or intergrade populations (or both) were observed at superoxide dismutase-2 and α-glycerophosphate dehydrogenase-A (loci with previously described variability), and at adenosine deaminase, alcohol dehydrogenase, galactose-1-phosphate uridyltransferase, and mannosephosphate isomerase. Variation restricted to northern largemouth bass and intergrade populations was observed for malate dehydrogenase-1 (previously reported), peptidase-3, and triosephosphate isomerase-2.