Etomidate was tested as an anesthetic on channel catfish Ictalurus punctatus, golden shiners Notemigonus crysoleucas, and bluegills Lepomis macrochirus. The 24-hour median lethal concentration (LC50) at various temperatures was lowest for bluegills (0.61–0.68 mg/liter) and highest for golden shiners (1.87–2.73 mg/liter). Generally, etomidate was more toxic, and induction of anesthesia and recovery from anesthesia were slower, at 17 C than at 22 and 27 C. Water hardness and pH had no or only slight effect on the toxicity and efficacy of etomidate. All channel catfish in 8 mg/liter and all golden shiners in 10 mg/liter were anesthetized within 2 minutes at 22 ± 1 C (±range) and all survived if removed from the etomidate immediately after opercular movement stopped. Both channel catfish and golden shiners were anesthetized within 15 minutes by 3 mg/liter, and all of the fish survived at this concentration for 30 minutes. Concentrations of 0.2 and 0.4 mg/liter sedated channel catfish, and 0.4 and 0.6 mg/liter sedated golden shiners. The safety index LC50/EC50 (median effective concentration) for anesthesia of channel catfish and golden shiners at 22 ± 1 C decreased from 6.2 to 5.0 and 7.6 to 4.0, respectively, as exposure length increased from 10 to 80 minutes.