This comparative study of growth performances and sexuel growth dimorphism was conducted with fish obtained from artificial reproduction. Growth was measured weekly. The levels of sexual steroids (11-KT) and thyroid hormones (T3 and T4) was measured after 74 rearing days and at the end of the experiment (103 days). Social interactions were examined with a video camera (three sequences of one hour for each group). #O. niloticus# and #S. melanotheron# achieved the best and worst growth rates, respectively, with their intergeneric hybrides standing in between. Tilapias originating from female #O. niloticus# (pure species and hybrid 1) exhibited a significant sexual growth dimorphism, which contrasted with the situation observed in the two other groups (originating from female #S. melanotheron#), where no significant difference was measured. Male tilapias from the two hybrid groups had similar growth rates, whereas hybrid females originating from female #S. melanotheron# (hybrid 2) grew faster than those coming from female #O. niloticus# (hybrid 1). The levers of 11-KT were highest in #O. nioticus# and lowest in #S. melanotheron#. The levels in the hybrid groups were similar and intermediate between those of the pure species. By contrast, the lever of T4 was highest in #S. melanotheron#. The levels of T3 at 74 days did not differ between groups but between sexes in all four groups. At the end of the experiment, this sex-related difference was still observed in the hybrid 2 group whilst it had vanished in the hybrid 1 group. The analysis of behavioural sequences indicated that aggressive behaviours (face to face or jaw to jaw interactions, attacks with or without poursuit) first emerged among faster growing fish (#O. niloticus# and hybrid 1)