We studied several biological parameters of Trichogramma pretiosum Riley and T. brassicae Bezdenko using Plutella xylostella (L.), and Trichoplusia ni (Hübner) eggs as hosts in the laboratory. Developmental times (days) from egg to adult emergence were not significantly different between the two parasitoid species. Both parasitoid species parasitized more Trichoplusia ni eggs than P. xylostella eggs with similar rates of parasitism between the two parasitoid species. However, T. pretiosum parasitized more P. xylostella eggs than T. brassicae did. More parasitized T. ni eggs eclosed than parasitized P. xylostella eggs. The egg eclosion rates of both host species parasitized by T. pretiosum were higher than those by T. brassicae, whereas, the eclosion rate of P. xylostella eggs parasitized by T. pretiosum was significantly higher than those by T. brassicae. More parasitoid wasps emerged from a single parasitized T. ni eggs than from a single parasitized P. xylostella egg with no significant differences between the two parasitoid species. There were no significant differences between the longevities of the female or male adults of either parasitoid species emerged from either host species. The female and male T. pretiosum adults emerged from the eggs of both host species lived >2-fold longer than T. brassicae. Both parasitoid species produced significantly more females (69.6-97.5%) than males with no significant difference between the two host species. T. brassicae produced more females than T. pretiosum in the eggs of both host species.