With the object to advocate new promising cross breeds (hybrids) of Bombyx mori.L. specific to Rayalaseema region of Andhra Pradesh for commercial exploitation, this book is now brought out which includes the silkworm breeding technique to identify new multi x bivoltine hybrids of silkworm Bombyx mori .L. This book speaks about the performance of multivoltine and bivoltine new silkworm races evaluated in different seasons with regard to the expressions of the economic traits; adjudication of promising silkworm hybrids by employing Line x Tester analysis for hybrid testing ; and evaluation of silkworm hybrids at farmers conditions.