Rainbow trout (Salmo gairdneri) were fed 38% protein experimental diets which contained either sunflower or soybean meal. Fish were reared in 2 sets of tanks under controlled and ambient water temperatures during January-April 1982. With controlled water temperature, fish fed the sunflower meal diet had a significantly higher final weight, average gains and food conversion ratio. Under ambient water temperature conditions, trout fed sunflower meal diet also had significantly higher final weight and average gain than trout fed soybean meal diets. A 35% protein sunflower meal adequately replaced a 49% protein soybean meal as a protein source in rainbow trout diets.