Iwashi-nukazuke, salted sardine cured in rice bran, is one of the traditional fish products of Japan and a study was carried out to investigate the changes in texture of sardine meat during curing. The firmness of the fish meat, as measured by a texturometer, decreased gradually, and the fragility, as measured by a fragility test devised by us, increased during curing. The physical changes that were monitored during curing by a sensory evaluation coincided with those by the objective tests. SDS-PAGE patterns for the fish meat proteins indicated that the myosin heavy chain of sardine muscle was decomposed into fragments of smaller molecular size. This protein decomposition seems to have been caused by the action of enzymes in the rice bran (nuka) and in the malt (koji). The changes in meat texture during curing thus seem to be caused by the decomposition of fish meat proteins.