The main objective of silkworm breeding is the progressive improvement of economic traits to increase the profit of silk producers and other sectors of the sericulture industry. There are approximately 2000 different strains of Bombyx mori used in silk production worldwide (Reddy, 1986). Twenty one characters influence silk yield quantitatively or qualitatively (Chateerjee et al., 1990). The use of selection indices for genetic and economic improvement of traits in the shortest time will give the greatest improvement (Harris, 1970). Several researchers have shown the heritability of these characteristics in mulberry silkworm. The general aim of selection in animal breeding is to acquire new generation of animals which, under future economic conditions of the production system, are more efficient than the present generation. The goal of the present study is investigation of individual selection based on cocoon weight in comparison to randomize selection in two lines of mulberry silkworm (31 and 32) and its effects on production traits of their hybrid (31×32).