The influence of Ca2+ concentration around myofibrillar Mg2+-ATPase on the speed and pattern of rigor mortis in fish species or cultured and wild fish was studied. The change of contraction in pillar form muscle with the lapse of storage time reflected very well the temporal change of gram of tension in muscle of cultured red sea bream. This result showed that the contractile percentage of muscle is very useful on the progress of rigor mortis. The progress of muscular contraction differed among fish species and between cultured and wild fish of the same species, and which were seen in four parameters of rigor mortis: the progressive speed, pattern, and the time and level of peak reached. These four parameters were closely related to one another.The ranking among fishes in myofibrillar Mg2+-ATPase activity was not consistent with the difference of speed of progression of muscular contraction. The progress of superprecipitation reaction of actomyosin in muscle of cultured red sea bream was changed remarkably in four parameters by a very small difference of Ca2+ concentration, coinciding very well with the mutual relation among the four parameters on the progress of muscular contraction. Therefore, it was considered that the difference of the progress of muscular contraction among fish species and between cultured and wild fish can be mainly caused by the difference of Ca2+ concentration around myofibrils.