Technical Abstract: Heritability of body length and body weight was evaluated in 44 families of hybrid striped bass raised in replicated indoor tanks to 42 days post hatch. Fingerlings averaged 36.7 (' 2.6 SD) (range 27.7-45.3) mm and 0.53 (' 0.10) (0.22-1.22) g across all families after 42 days of indoor rearing. Analysis of variance demonstrated highly significant differences in length and weight of fingerlings among different paternal and maternal half-sib families (P < 0.0001). There were significant sire and dam components of phenotypic variance for both traits, with the dam component of variance higher than the sire component. Corresponding estimates of heritability were between 0.67 and 1.11 for dams and 0.44 and 0.48 for sires. These results indicate that a substantial portion of the selection differential would be expected to be gained in the offspring of the selected pure-line parents in an interspecific selective improvement program. By determining genetic parameters at multiple life stages, appropriate selection criteria can be developed at the earliest possible time during the production cycle.