Abstract : The aquatic toxicity of a secondary alcohol, 3,3-dimethyl-2-butanol Pinacolyl Alcohol (PA), was determined. Acute tests were conducted on Pimephales promelas, 48 hr EC50 = 443.1 mg PA/1, and Daphnia magna, 24 hr EC50 = 513.2 mg PA/1. Growth inhibition tests (96 hr) were conducted using Ankistrodesmus falcatus, EC50 = 257.7 mg PA/1. In general, the toxicity of straight-chained alcohols increases proportionally with the molecular weights. Using the structure activity equation (Log EC50 = 1.10 (LogP) + 0.05 (LogP)squared - 1.22) for P. promelas, the calculated toxicity of PA (EC50 = 547.0 mg/1) agrees with experimental determinations.