Turbot, Scophthalmus maximus (L.), and sea bass, Dicentrarchus labrax (L.), are susceptible to vibriosis. a septicaemia caused in France by Vibrio anguillarum 408. A bacterin produced with this strain by Rhone-Mcrieux has been tested orally in both species and, as a con\parison, by intraperitoneal injection. During a ehallenge carried out 4 weeks later by intraperitoneal inoculation, the protection observed in orally vaccinated fishes was significant (72 % in sea bass and 70 % in turbot). Eleven weeks after vaccination, this protection is still significant. The mean titre of serum agglutinins was weakly inereased in orally vaccinated fishes. Bacteriostatic antibodies have also been searched for in serum, but compared to agglutination, the applied technique leads to lower titres and it has not been possible to prove the presence of sueh antibodies after oral vaccination. Passive immunizations using serum from orally vaccinated fishes {2 months after vaccination) confers some protection against a challenge carried out by inoculation of virulent vibrio. Therefore, the production of serum factors following oral vaccination of sea bass and turbot may be involved in generalized protection of fish.