An Arthrobacter sp. growing on 4-Chlorobenzoic acid as its sole source of carbon excretes 4-hydroxygenzoic acid and protocatechuic acid into the culture medium. Protocatechuic acid is further attacked by "meta"-cleavage. During growth of the Arthrobacter sp. on benzoic acid cis-cis muconic acid can be isolated from the medium, suggesting the involvement of the "ortho"-cleavage pathway. The enzymes both for the "meta"- and the "ortho"-cleavage pathway are inducible.