The TLm for bluegill and redear sunfish was determined in the laboratory using standard bioassay procedure and water from two sources. A considerably larger concentration of antimycin was required to kill fish of the same size under field conditions. Probable reasons are discussed. Selective kills of bluegill and redear were attempted in the field under pH values ranging from 6.4 to 9.6. The antimycin concentration required under these various conditions is discussed. Total kills following selective kills showed size selectivity as well as species selectivity.