Males of two strains of carp, wild Duna (D), and inbred Szarvas 22 (22), were selected for high and low stress response. Two purebreds of D and 22, from randomly chosen parents and four crosses, 22 x 22-L (low stress response), 22 x 22-H (high stress response), 22 x D-L (low stress response) and 22 x D-H (high stress response) from selected stress response parents were produced and vaccinated with a commercial Aeromonas salmonicida/Aeromonas hydrophila vaccine and their circulating antibody response evaluated 1, 3, 5, and 7 weeks post-vaccination by ELISA. Significantly higher titres of circulatory antibodies against A. hydrophila were found in the families 22 and cross 22 x 22-L compared to other groups. The development of circulatory antibodies against A. hydrophila in all crosses having at least one D parent was low and remained low throughout the experiment. The level of circulatory antibodies against atypical A. salmonicida in the inbred strain increased following a booster vaccination with the highest values measured in inbred strain 22 and cross 22 x 22 L. The different varieties of carp had different levels of survival against experimental challenge with A. hydrophila. The greatest survival was obtained in strain 22 and cross 22 x 22-L, while ~90% of D wild carp and cross 22 x D (independent of their stress response) died. Survival results correlated well with the antibody response of the different groups: 22 and 22 x 22-L had the highest antibody titres against A. hydrophila and the greatest level of survival.