The aim of this study was to determine the effects of different cooking methods on the electrophoretic patterns of rainbow trout (Oncorhynchus mykiss) fillets using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Raw rainbow trout were deep-fried, microwaved, grilled, and baked and then monitored for changes in the electrophoretic pattern. All cooking methods resulted in significant moisture loss when compared to the raw sample (P < 0.05). Water losses, occurring during cooking resulted in a higher protein content in all of the cooked fish, with regard to raw fish. Deep fried fish had higher lipid content than raw or other cooked fish. The electrophoretic pattern of samples showed a considerable number of protein bands. The bands did not disappear completely, but changed remarkably after cooking. Considering myosin and actin bands, the highest rate of bands disappearance was observed with microwaved sample, while the lowest rate occurred with deep-fried sample.