Several experiments were conducted on relationships between oxygen consumption of channel catfish (Ictalurus punctatus) and environmental dissolved oxygen concentrations, feeding status, weight of fish, and temperature. Estimates of oxygen consumption under culture conditions were obtained by determining the rate of oxygen depletion in a still tank without aeration. Respiratory dependence (decrease in oxygen consumption rate with a decrease in environmental oxygen concentration) in both well-fed and fasted fish was noted at oxygen concentrations between 1 and 7 milligrams/liter. The oxygen consumption rates obtained one hour after feeding were higher than those taken immediately after feeding or from fasted fish. A log-log relationship between oxygen consumption and body weight of fish (2.3-1,006 g) was demonstrated. The slope (b) for the equation, oxygen consumption = (a) (weight)bwas 0.80 for both well-fed and fasted fish. The relationship between oxygen consumption and environmental temperature was linear over the range 24-28 C for well-fed fish and 24-30 C for fasted fish. The Q10's for plots for the well-fed and fasted fish were 1.9 and 2.3, respectively; thus the data were in accord with van't Hoff's Law.