An NADP-dependent alcohol dehydrogenase was purified to homogeneity from Acinetobacter sp. strain HO1-N. The enzyme appears to be a tetramer of sub-unit M(r) 40,600, and it has kinetic and other properties almost identical to those of an enzyme previously isolated from Acinetobacter calcoaceticus strain NCIB 8250. The alcohol dehydrogenases from both of these strains of Acinetobacter oxidized primary alcohols. The highest k(cat(app)) values were with alcohols containing from four to eight carbon atoms; there was activity up to tetradecan-1-ol, although it was a poor substrate, but there was no measurable activity with hexadecan-1-ol. The highest specificity constant was found with hexan-1-ol as substrate when the measurements were made in the absence of dioxan, and with decan-1-ol as substrate when assayed in the presence of dioxan. It seems unlikely that this enzyme is involved in the metabolism of wax esters or of long-chain alkanes.