This experiment was conducted to compare physico-chemical properties of rainbow trout muscle between purebred and crossbred, pond fish and silo fish, and between sexes. The results obtained were as follows : 1. More pigmentation was observed in pond fish muscle than in silo fish muscle (p$lt;0.01). 2. Heavy fish muscle tended to have more pigmentation than light fish muscle (p$lt;0.01). 3. Crossbred fish muscle had less pH₁-difference between pH₁-value (15 minutes post mortem) and pH₂-value (24 hours post mortem) but higher water-holding-capacity (WHC) than purebred fish muscle, and silo fish muscle showed the same trends compared with pond fish muscle (p$lt;0.01). 4. No significant differences were observed in pH-values, WHC and chemical compositions of fish muscle between sexes. 5. Significant differences between silo fish muscle and pond fish muscle were observed in the contents of chemical components such as dry matter, fat, protein and ash (p$lt;0.01). 6. Dry matter and fat contents tended to increase with increasing body weight (p$lt;0.05), while protein and ash contents remained unchanged. 7. The pH-difference was larger, and WHC was lower in the fish of higher body weight (p$lt;0.05).