Data from annual gillnetting surveys were used to determine sizes, age structure, and relative growth of an introduced population of blue catfish in Lake Oconee, Georgia. Age and back-calculated growth were estimated with three determination-techniques and compared for precision. Blue catfish catch increased from 1997 to 2009; there was a concurrent decline in catch of native white catfish. Blue catfish ages ranged from 1 to 8 years old (mean=3.7 years, SD=1.4 years) and annual relative growth was 86.1 mm (SD=36.1 mm). Age assignment-precision was highest for otoliths (83.5%) and lowest for basal recesses (71.4%). Mean back-calculated total lengths were significantly variable among fish from ages 1-3 for each technique compared. Otoliths produced smaller estimates for mean total length from ages 1-6. The blue catfish population in Lake Oconee is relatively young and individuals are growing rapidly; otoliths and articulating processes of pectoral spines suffice for blue catfish age determination.