The chemical, 2-(digeranylamino)-ethanol, was tested in the laboratory and in outdoor plastic pools to determine the toxicity to a variety of cold- and warmwater fish. An interesting aspect is that the toxicant is more toxic to carp (Cyprinus carpio) than to other warmwater fish. The 96-hr LC50 (concentration producing 50% mortality) for carp is 0.0507 mg/liter, whereas that value for centrarchids ranges from 0.237 mg/liter for smallmouth bass (Micropterus dolomieui) to 0.720 mg/liter for bluegill (Lepomis macrochirus). The toxicant is significantly less toxic (P = 0.05) to bluegill in cold water (12 C) than in warmer water (17 and 22 C), and it is more toxic in hard water than in soft water. Toxicity tests with green sunfish (Lepomis cyanellus) show that the toxicant is significantly more toxic (P = 0.05) in high pH water (pH = 9.0) than in low pH water (pH = 6.0), and the toxicant detoxifies at a faster rate in pH 9 than in lower pH water. Some aquatic invertebrates are more resistant than fish to the toxicant. The chemical is a good candidate selective toxicant, but additional studies are needed to support a registration for its use.