Antimycin was applied to five fresh-water ponds at 3, 4, or 5 ppb, and to two salt-water ponds !lit 10 ppb. Undesirable fish, including four centrarchids and one cyprinid, were eliminated from four of five freshwater ponds. Undesirable fish, including a centrarchid and a livebearer, were eliminated from both salt-water ponds. Mosquitofish, Gambusia affinis, were killed in five ponds, but were eliminated in none. Channel catfish, Ictalurus punctatu8, that were in four ponds, were not killed. Antimycin showed real promise as a fish toxicant particularly for removing trash fish from catfish ponds. Antimycin, under the trade name fintrol, is registered as a fish toxicant by the Food and Drug Administration and by the U. S. Department of Agriculture. The retail cost to treat one acre-foot of water with 3 ppb antimycin was approximately $4.50.