Three batches of rabbits were immunized against 2 strains of Vibrio anguillarum (Va V 62 and Va V 408), which cause vibriosis in sea bass Dicentrarchus labrax (L. 1758) Serranidae. Homologous and heterologous reactions were obtained against these Vibrio strains and other bacteria using an improved indirect ELISA technique. Antibody and antigen titrations revealed high immunogenecity (high antibody titers for the antisera) of the 2 Vibrio strains. They correspond to serotype I and show close affinity. The specificity and sensitivity of 1 selected antiserum were tested on brain extracts from healthy sea bass and those infected artificially with V. anguillarum serotypes I and III. Preliminary results confirm the reliability of the technique and warrant its use for improving disease diagnosis.