The enantioselective reductions of aryl alkyl ketones, ArC(O)R, with a diverse number of alkyl groups have been achieved with an isolated carbonyl reductase from Sporobolomyces salmonicolor. Of special interest is the observation that ketones with sterically bulky alkyl groups could be reduced to the corresponding alcohols in excellent optical purity. An unusual alkyl chain-induced enantiopreference reversal was observed but was shown to be consistent with the enzyme-substrate docking calculations.