An experiment was initiated to evaluate hybrid vigour in twelve F$_1$ hybrids and seven three-way crosses of multivoltine ${ imes}$ bivoltine silkworm between newly evolved multivoltine breed BL67 with productive bivoltine CSR breeds and hybrids. Analysis of variances computed for different characters among F$_1$hybrids and three-way crosses showed highly significant differences among them indicating presence of both additive and non-additive gene actions for the expression of these characters. Among twelve F$_1$ hybrids, two F$_1$ hybrids viz., BL67${ imes}$CSR$_4$and BL67${ imes}$CSR$_{5}$ have expressed significant heterosis for nine characters and two hybrids viz., BL67${ imes}$NB$_4$D$_2$and PM${ imes}$NB$_4$D$_2$ for eight characters whereas out of nine three-way crosses, three hybrids viz., BL67${ imes}$ (CSR$_3$${ imes}$CSR$_{6}$), BL67${ imes}$(CSR$_{16}$${ imes}$CRS$_{17}$) and BL67${ imes}$(CSR$_{18}$ ${ imes}$CSR$_{19}$) expressed significant heterosis for eight characters. In the present study, it is observed that the cocoons of two hybrids viz., BL67${ imes}$CSR$_4$and BL67${ imes}$CSR$_{19}$ were found to be uniform as these hybrids showed lowest CV％ (5.35 and 5.38) among twelve F$_1$ hybrids and seven three way crosses between multivoltine ${ imes}$ bivoltine hybrids. Four F$_1$ hybrids viz., BL67${ imes}$CSR$_4$, BL67${ imes}$CSR$_{5}$, BL67${ imes}$ (CSR$_3$${ imes}$CSR$_{6}$), BL67${ imes}$(CSR$_{16}$${ imes}$CRS$_{17}$) and BL67${ imes}$(CSR$_{18}$ ${ imes}$CSR$_{19}$) showed superiority in expressing hybrid vigour and are considered as best heterotic hybrids for commercial exploitation.ion.ation.ion.ation.ion.