ABSTRACT: We used laboratory and field studies to compare the substrate- and habitat-specific behavior and survival of hatchery-reared (HR) versus wild juvenile summer flounder (Paralichthys dentatus) and make inferences about the biological feasibility and economic cost of stock enhancement success with this species. We then created a model to predict optimal release scenarios (maximum survival at minimum costs) under varying sizes at release, dates of release, and numbers released. In laboratory trials, HR fish spent significantly more time swimming in the water column, took significantly longer to become cryptic on the benthos, and were significantly more susceptible to predation than wild fish. Anti-predator conditioned HR fish suffered significantly lower predation-induced mortality than naïve HR fish. In field experiments, released HR fish exhibited poor survival compared to wild fish. Caging and tethering trials, coupled with the laboratory trial data, suggest that the poor survival of HR fish in the wild was a result of increased susceptibility to predation, as compared to wild fish. Model simulations of varying release scenarios of HR fish suggest that optimal stock enhancement results will be obtained when relatively large fish are released early in the season. Depending on post-release density, various density-mortality relationships considerably affected predicted post-release survival and costs associated with enhancement efforts, but did not alter the release scenario that produced optimal results. These results indicate that knowledge of density-mortality relationships is important to quantitatively predicting results of stock enhancement efforts, but not to predicting the release variables that will optimize results. Economic calculations suggest that enhancement efforts that successfully accomplish management goals may be extremely costly for summer flounder, but costs must be compared with predicted costs of alternative management methods to determine if stock enhancement is a recommendable fisheries management tool.