Rhodococcus erythropolis Y2 produced two types of dehalogenase: a hydrolytic enzyme, that is an halidohydrolase, which was induced by C3 to C6 1-haloalkane substrates, and at least one oxygenase-type dehalogenase induced by C7 to C16 1-haloalkanes and n-alkanes. The oxygenase-type activity dehalogenated C4 to C18 1-chloroalkanes with an optimum activity towards 1-chlorotetradecane. The halidohydrolase catalysed the dehalogenation of a wide range of 1- and alpha,omega-disubstituted haloalkanes and alpha,omega-substituted haloalcohols. In resting cell suspensions of hexadecane-grown R. erythropolis Y2 the oxygenase-type dehalogenase had a specific activity of 12.9 mU (mg protein)-1 towards 1-chlorotetradecane (3.67 mU mg-1 towards 1-chlorobutane) whereas the halidohydrolase in 1-chlorobutane-grown batch cultures had a specific activity of 44 mU (mg protein)-1 towards 1-chlorobutane. The significance of the two dehalogenase systems in a single bacterial strain is discussed in terms of their contribution to the overall catabolic potential of the organism.