Thirteen Oklahoma reservoirs (<120 ha) containing northern largemouth bass (Micropterus salmoides salmoides) populations were stocked with Florida largemouth bass (M. s. floridanus) for 3 years. Stocked and native fish were identified phenotypically by electrophoresis. Stocked fish made up an average of 15% of each year class in the fall at age 0, but the mean proportion declined to 5% by the following spring. Relative overwinter survival to age 1 averaged 25%. Florida largemouth bass were significantly longer at age 0 and age 1 than the northern subspecies but had significantly lower mean relative weights. Survival, mean length, and mean relative weight of Florida phenotypes were lowest in study lakes in the northern and western portions of Oklahoma, indicating that climatic factors were very influential. A recommendation was made to discontinue Florida largemouth bass stockings in Oklahoma north of a diagonal boundary from southwest to northeast. This would limit stockings of hatchery production to areas of the state that show the greatest potential for producing trophy bass.