Vertebral deformity, kyphosis and lordosis, occurred in cultured marine fishes, yellowtail (Seriola quinqueradiata) and amberjack (Seriola dumerili) with higher frequency than usual in 1999 in farms at Kagoshima Bay, Kyushu Island, Japan. The cause of deformity was not thought to be involved in infection with bacteria and parasites. Furthermore, fenobucarb, an agricultural pesticide, was not detected from the musclature. Morphological characteristics observed in the body and vertebra of yellowtail included two kinds of deformities, one was kyphosis at the center part of body, and another was lordosis at caudal portion. The latter was similar to that reported previously in other prefectures. In the case of amberjack, two types were observed. One was similar to that observed in yellowtail, though some differences were observed in the body site of occurrence and the degree of deformity. Another one is clearly different from that of yellowtail showing remarkable lordosis at the center part of body. The possible cause of the difference in the observed deformity between yellowtail and amberjack may be attributed to the difference in the structure of vertebra and the origin of seeds, wild or hatchery-produced.