This study was to determine the effects of changes that occurred in the muscle proteins of fresh rainbow trout (Oncorhynchus mykiss) fillets during storage at 4 +/- 1 degrees C as a result of packaging in vacuum (C), subject to high pressure after packaging in vacuum high hydrostatic pressue (HHP), packaged in vacuum after wrapping with chitosan film (CFW) and subject to high pressure after wrapping with chitosan-based film and packaged in vacuum (HHP+CFW ). Samples were subjected to SDS-PAGE in four-day intervals and the densitometric analyses of the gels were carried out. According to the results, minor changes were determined in the major bands of the sarcoplasmic and myofibrillar muscle fractions of trouts as a result of HHP application and CFW. The most important change occurred in the myofibrillar muscle fraction as a decrease in the densities of the bands at 200 and 31.4kDa after HHP application. Similarly, the sarcoplasmic muscle fraction of trout fillet decreased in the densities of the bands at 39.3, 26.6 and 23.3kDa after HHP application. In addition, it is thought that the bands that occur at 30kDa in the myofibrillar muscle fraction and at 20.7kDa at the sarcoplasmic muscle fraction may be related with the degradation of trouts during cold storage.