In the present work an attempt has been made to study total Cu-Zn SOD (Super oxide dismutases) activity (Units.mg-1 protein) in the liver of Labeo rohita (Ham.) collected from six different experimental sites (namely River Sone, River Koshi, Near Saharsa, River Ganga at Buxar, Patna, Mokama and Barh). Total SOD (antioxidant defence system) in liver were lowest at Buxar and Patna site of river Ganga and highest at Barh. Cu-Zn SOD were lowest at Buxar and highest at Barh. Mn-SOD activities were lowest at Patna and highest at Barh. The reason for such variations in SOD activities in liver tissues in a fresh water major carp, Labeo rohita (Ham.) has been discussed in detail in this paper.