were observed in surviving fish, and no bacteria were isolated fromthese fish.Efficacy of the vaccine was evaluated in the field. Because of bio-logical problems and legal limitations, only antigens mixed withISA763A were intraperitoneally injected into groupers. The protec-tion observed in the field trial was similar to that achieved in thelaboratory. Mortality was 73.3% in the control group and 1.1% inthe vaccinated group at 1 month PSV (Table 1). Dead fish exhibitedsigns of streptococcosis, and S. iniae could be re-isolated from alldead fish in the control group (Table 2). No clinical signs of strepto-coccosis were observed in the surviving fish, and no bacteria wereisolated from these fish. Moreover, RPS was 98.5% in the vaccinatedgroup and remained high after challenge with S. iniae (108CFU