Channel catfish, Ictalurus punctatus (Rafinesque) exhibited changes in levels of muscle and blood electrolytes during recovery from short-term hypoxia. Ten minutes of confinement in water having zero mg/liter oxygen resulted in an acidosis characterized after 1 hr of recovery by elevated blood lactate, decreased blood pH, and an increase in plasma osmolarity and hematocrit. Muscle water content was increased at this time. Later changes in these parameters appeared to be influenced by season or temperature. Plasma osmolarity dropped below control levels in June and remained depressed after 36 hr of recovery. In August plasma osmolarity fluctuated at levels above control values and had not returned to normal after 48 hr. These data indicate that electrolyte imbalance persists for many hours after blood lactate has declined to control levels and this imbalance may limit the fish's ability to tolerate further stress.