Growth and survival were determined for duplicate lots of juvenile channel catfish (Ictalurus punctatus) and yellow perch (Perca flavescens) exposed for 69 and 67 days, respectively, to nearly constant dissolved oxygen (DO) concentrations at near air saturation (control), 6.5, 5.0, 3.5, and 2.0 mg/l. The following year juveniles of the same species were exposed to DO concentrations that gradually fluctuated diurnally at about 1.0 to 1.5 mg/l above and below the constant lowered DO levels of the previous year. At mean constant DO concentrations of 3.5 mg/l or less, channel catfish consumed less food and growth was significantly reduced. Survival of both species was unaffected by the reduced DO exposures.