1. 1. A membrane-bound alcohol dehydrogenase (alcohol:(acceptor) oxidoreductase, no EC number) has been solubilized from Pseudomonas aeruginosa by treatment with Triton X-100 and purified to homogeneity as judged by electrophoresis on polyacrylamide gels. (Spec. act. 6.4 units/mg protein for 1-octanol.) Aggregation of the enzyme takes place in the absence of detergent. This may be at least partly related to the lack of stability of the purified enzyme. 2. 2. The purified enzymes does not use pyridine nucleotides (NAD or NADP) as coenzymes. No spectral evidence of the involvement of a flavin as a prosthetic group has been found. Among the artificial electron acceptors tested, only phenazine methosulfate is utilized. The product of oxidation of an alcohol is the corresponding aldehyde. 3. 3. This alcohol dehydrogenase has a high affinity for long chain primary alcohols ( K m for 1-tetradecanol 4.5 μM). It is induced by growth on various hydrocarbons and especially by long-chain hydrocarbons ( n- hexadecane ). These properties clearly indicate its involvement in the degradation of long chain hydrocarbons in P. aeruginosa.