Copepods are among the best biomarkers for trace metals monitoring in marine environments, because of their huge biomass, limited swimming capacity, vital role in the trophic food chain, sensitivity to trace metal contamination, and easy availability. This study presents the results of trace metal investigations (Cd, Cr, Cu, Fe, Mn, Pb, and Zn) in copepods and in seawater, in an oceanic outfall area and at two background stations off northern Taiwan. The results show that copepods collected at the ocean outfall stations were less diverse but more abundant than those at the background stations. The concentration ranges of trace metals in copepods at all stations were as follows: Cd, 0.54-1.48 mu g/g; Cr, 43.6-158.7 mu g/g; Cu, 43.4-129.2 mu g/g; Fe, 921-4438 mu g/g; Mn, 28.4-64.7 mu g/g; Pb, 10.7-33.6 mu g/g; Zn, 819-2335 mu g/g. The concentrations of trace metals in copepods varied with the various species. With the exception of dissolved Cu, the differences in trace metals in the dissolved phase and in copepods at the study stations were minor. However, the concentration of dissolved Cu at the outfall stations was nearly four-fold higher than that at the background stations. The mean increase in bioconcentration factor of copepods for trace metals followed the sequence: Fe(6.0) > Zn(5.7) > Pb(5.6) > Cr(5.5) > Cu(5.0) > Cd(4.9) > Mn(4.8). This result suggests that copepods have a great capacity to accumulate trace metals.