Senegales sole, Solea senegalensis, adult specimens were subjected to sublethal copper exposure (100 microg SO(4)Cu/L) for 7 days (contamination period) and afterward kept for 4 days without copper exposure (depuration period). In contaminated and detoxified specimens, the hepatocytes indicated a great number of lipid droplets compared to the control specimens. Some ultrastructural alterations such as partial disruption of the microvilli and endothelial lining of the sinusoids were observed in the hepatocytes. Lifting and swelling of the lamellar epithelium were common lesions in S. senegalensis gills due to the copper exposure. On the other hand, in contaminated and detoxified specimens, gills demonstrated separation of respiratory epithelium; chloride and pavement cells were also altered. Copper levels in gills, and especially in liver, increased during sublethal copper exposure (up to 7 days). During the detoxification period, Cu concentrations in gills and liver experienced variable changes. The results of the study indicate that histology is a successful tool capable of revealing sensitively and selectively even the sublethal effects of heavy metals on the environment and aquatic biota.