The study was to investigate the adaptation, habitat preference and seaward migratory behavior of the cultured Japanese eel, Anguilla japonica, after they were released to wild environments. From September to October of 2003, 1270 cultured eels were released into both south and north coasts of Dapong Bay, and upstream and estuary of Kao-Ping River. The recapture rates of large (1,200 g) and medium-sized eels (400 g) in Dapong Bay were 19.3% and 11.8%, respectively; in Kao-Ping River, the recapture rate was only 2.4% in estuary area. The total mean recapture rate was 11.2%. Those eels released in the upstream of Kao-Ping River were not captured in the estuary. Among the recaptured eel in Dapong Bay, 85.2% were caught in location of the first tidal trough where has freshwater discharge or low salinity environment. This seems to reflect that the characteristics of natural life history of yellow eels tend to up-stream and inhabit at freshwater environment. In addition, the decrease in body weight after the release was probably due to poor adaptation to the new environment or low feeding rate in low water temperature.