To investigate the effects of environment on tissue norepinephrine (tNE) levels of fish, we examined tNE concentrations in the adult chum salmon (Oncorhynchus keta) from fresh water (FW) and from sea water (SW). Plasma norepinephrine (pNE) and tNE of 15 organs, including the gill, heart, liver, aorta, spleen, stomach, jejunum, colon, brain stem, cerebrum, muscle, bone, sexual organ and kidney (head and body), were determined in river and sea salmon by high performance pressure liquid chromatography with electrochemical detection. tNE concentrations of all organs except the gill of sea salmon were significantly lower in comparison with those in river salmon. The pNE concentration was higher in sea salmon than in river salmon of male but not female. In river salmon, tNE concentrations of 12 organs of females were higher than those of male, whereas in sea salmon, there was no significant difference in tNE concentrations of all organs except the liver between male and female. Plasma osmolality and sodium concentration were higher in sea salmon than in river salmon. These results indicate that tNE concentrations in most organs of salmon in a SW environment are significantly decreased compared with those in a FW environment, and that tNE concentrations are higher in female salmon than in male salmon in a FW environment but not in a SW environment.