The anesthetic, biochemical and pathological effects of eugenol were evaluated in the African cat-fish Clarias gariepinus in comparison with MS-222. Aquous exposure of Clarias gariepinus to eugenol at concentration of 62.5 – 250 ) g / ml showed short interval to induction than MS-222. On the other hand, eugenol provided longer time for recovery (8.28 min) at higher concentration (250 )g / ml) than MS-222 (5.26 min) but no differences were observed at lower concentrations between both agents. Mortality rate of 46.5 and 33.3 % was recorded for eugenol and MS-222, respectively at 250 )g / ml. Exposure of fish to 250 )g / ml of eugenol or MS-222 resulted in significant increases in serum levels of creatinine, urea and uric acid and decrease in total protein and albumin. Significant increases in AST, ALT and Ca levels were recorded only on exposure to eugenol 250 )g / ml. Histopathological examinations showed congestion of gill blood vessels, diffuse vacuolar degeneration and necrosis of the epithelium lining of the secondary lamellae of the gill filaments, degeneration and focal necrosis of renal tubules in kidneys, necrosis and deposition of hemosiderin pigment in the macrophages of spleen which is indicative for hemorrhages and hemolysis as well as mild catarrhal enteritis of intestine of fish groups exposed to 250 ) g / ml of both agents. Moreover, massive fatty and degenerative changes in liver were observed only in fish exposed to 250 )g / ml of eugenol. On the other hand, lower concentrations of both agents did not differ from those of control fish. In conclusion, it appears that eugenol at lower and medium concentrations could produce an anesthesia characterized by rapid induction and rational recovery without significant changes in tissues and blood chemistry. Care should be taken on using high concentrations of eugenol as ventilatory failure may occur