The combined effect of different temperatures (20, 25 and 30°C) and salinities (15, 25, 35 and 45 psu) on the specific oxygen consumption (CEO) in Litopenaeus vannamei was determined. For this, CEO of 248 organisms of different body sizes (0.31 to 15.85 g) was measured. The CEO decreased when shrimp weight increased in all treatments without presenting a definite pattern when the salinity increased; even though all the combinations of temperature and salinity did not statistically show slopes significantly different in the regression models for CEO and organism weight relationships. The slope values suggest that at 20°C there is high energy expenditure at 15 psu, and at 25°C the highest energy consumption occurs at 45 psu. Whereas at 30°C, the lowest energy consumption occurred combined with the lowest salinity (15 psu). This may indicate that the isosmotic condition (point of lowest energy expenditure) tends to change with temperature, which may imply that the shrimp can be cultivated at high temperature (30°C) and at low salinities (15 psu) without increasing energy expenditure.