The  genotoxic effects of cadmium chloride and arsenic trioxide was assessed singly and conjointly in  Oreochromis mossambicus (tilapia) with end points such as chromosome aberration, red blood cell anomaly , anomalous nuclei determination and sperm head anomaly detection.The  primary objective were to examine If cadmium chloride  and arsenic trioxide as well as ascorbic acid (AA) and ocimum, had, any genotoxic effect of their own on non target aquatic organisms and secondly if ascorbic acid and ocimum had any ameliorating effect on cadmium chloride  and arsenic trioxide induced genotoxicity in the fish, tilapia.key wordsChromosome aberration(CA),  genotoxicity,  mutation,  cell anomaly,  ocimum,  AA,  cadmium chloride,   arsenic trioxide.