The bioaccumulation pattern of copper (Cu) in gill, liver, kidney, and muscle of different sizes (fingerlings and adult age) of healthy Mystus vittatus when exposed to their respective sublethal concentrations of Cu-water, containing one-third 96-hr LC(50) level (6.20 and 15.95 mg L(-1)) for short-term (120 hr) and one-eighth 96-hr LC(50) level (2.33 and 5.98 mg L(-1)) for long-term experimentation, respectively, has been analyzed. The Cu shows a maximum deposition (p < 0.01) in the liver (82.12 and 70.65 microg/g) followed by gill (74.35 and 63.69 microg/g) and kidney (61.52 and 54.09 microg/g) both in fingerlings and adult fish, respectively, during 28 days of exposure. The lowest deposition of Cu is found to be 0.83 and 0.93 microg/g in fingerlings and 0.79 and 0.86 microg/g in adult muscle tissue during short-term (120 hr) and long-term (28 days) exposure periods, respectively. Comparing the accumulation of Cu on the two size groups at both exposure levels, it is obvious that the fingerlings showed higher Cu concentration in all tissues than those of adult fish. Another equally important finding is that the depuration of Cu by maintaining the bioaccumulated fish (long-term exposed group) of both size groups in quality dechlorinated ground water reveals that there is a significant (p < 0.05) reduction in Cu concentration in different tissues as the day passes. A comparison of the performance of the two size groups in respect of depuration clearly indicates that the fingerlings have taken 24-43 days (gill-kidney), whereas in mature fish it is 21-39 days (gill-kidney) to reach the level of control fish. Among the various tissues in both size groups, gill took the minimum number of days for complete recovery, whereas the muscle tissue did not significantly eliminate Cu even after 30 days of depuration. These data constitute a reference for future studies on the evolution of Cu accumulation and elimination tendency in relation to different size groups of fish in the ecotoxicological testing scheme for hazard assessment.