The investigation was conducted to evaluate the performances of rearing of eighteen races of silkworm, Bombyx mori L. Characters viz., weight of mature larva, number of cocoon kg-1, yield 100 dfls-1 (disease free layings), cocoon weight, shell weight, shell ratio and length of filament were evaluated in a single rearing season. Performances of the race BSR-BN (B1) were reasonably good for no. of cocoon kg-1, cocoon weight and shell ratio. BSR-BN (M) showed the highest rearing performance for shell weight but the BSR-ISK and BSR-BN (P) M were good for yield and length of filament, respectively. On the other hand, the race Nistari (G) was poor for cocoon weight and shell weight and the races Nistid white (P), BSR-BN (B1), Nistari (P), BSR-I (M) and BSR-IK (M) showed poor rearing performances for weight of mature larvae, shell weight, shell ratio, length of filament and yield 100 dfls-1 respectively in this investigation. Analysis of correlation conducted on the results of the experiment indicated that the characters of the races were correlated with yield non-significantly. Negative correlation between yield 100 dfls-1 and no. of cocoon kg-1 showed higher yield improvement which would be a good combination for an improved method of silk production.