To clarify whether the tenderization of fish muscle is due to the resolution of rigor, changes in the rigor index and breaking strength of muscle were examined as to plaice, parrot bass, yellowtail, carp, red sea-bream, striped grunt, tiger puffer, and rainbow trout. Upon storage at 5°C, most fishes reached maximal rigor within 24h after death. The maximal rigor continued within at least 72h after death and no resolution of rigor was observed within this period. Meanwhile, the breaking strength of muscle of all the fishes tested except for tiger puffer decreased sharply within 24h after death and then decreased gradually, although the values were markedly diverse between the fish species. These findings suggested that fish muscle tenderization proceeded independently of the rigor regardless of fish species.