Pseudomonas cepacia strain CMA1, which was isolated from soil, utilized 3-chloro-4-methylaniline (3C4MA) in concentrations up to 1.4 mm (0.2 g·l−1) as the sole source of carbon, nitrogen, and energy. In addition, 3-chloroaniline, 4-chloroaniline and phenol, but not aniline or methylanilines, were degraded by strain CMA1. Biodegradation of the anilines was coupled to the liberation of ammonium and chloride. The broad specificities of the aniline- and catechol-oxidizing enzymes were demonstrated in oxygen uptake experiments, which in addition showed higher activities for ring-cleaving than for aniline-oxidizing enzymes. Two ring-cleaving catechol 1,2-dioxygenases, which were induced selectively after growth on 3C4MA (pyrocatechase type II) and phenol (pyrocatechase type I), respectively, were discerned after partial purification by DEAE-cellulose chromatography.