Digestion rates have been measured for brown trout (Salmo trutta Linn.) during summer, fall, winter and spring seasons on the Blacksmith Fork River, Utah. Exponential rates of digestion varied from a gradual rate of -0.2372 to an accelerated rate of -0.6808. Factors found to affect digestion rate most were water temperature and the amount of food in the stomach. The affect of temperature was not clearly isolated. However, the amount of food in the stomach, at the beginning of the digestion study, appeared to have the most pronounced effect. Four of the five digestion rate measurements, with high coefficients 'of determination, were highly correlated to changes in the amount of food in the stomach. A stomach capacity study was also conducted during the winter season. A comparison of the results of the present study with those of an earlier study conducted during the summer season exhibited two nearly parallel non-linear regression lines. The differences in stomach capacity ranged from only 0.02 cc at 170 mm fork length to 0.93 cc at 340 mm fork length. Throughout the 170 to 340 mm size range, stomach capacities were smaller in the present study than those reported in the earlier study. Although some differences in method of determining stomach capacity did occur, these differences should have led to larger stomach capacities in this study. Since season of collection was different, it is suspected that was largely responsible for these differences. Therefore, the results of the stomach capacity study indicate that stomach capacities can be expected to change between summer and winter seasons. However, these changes may not be significant.