Pseudomonas sp. S-47 is capable of transforming 4-chlorobenzoate to 4-chlorocatechol which is subsequently oxidized bty meta-cleavage dioxygenase to prodyce 5-chloro-2-hydroxymuconic semialdehyde. Catechol 2,3-dioxygenase (C23O) produced by Pseudomonas sp. S-47 was purified and characterized in this study. The C23O enzyme was maximally produced in the late logarithmic growth phase, and the temperature and pH for maximunm enzyme activity were $30{sim}35^{circ}C$ and 7.0, respectively. The enzyme was purified and concentrated 5 fold from the crude cell extracts through Q Sepharose chromatography and Sephadex G-100 gel filtration after acetone precipitation. The enzyme was identified as consisting of 35 kDa subunits when analyzed by SDS-PAGE. The C23O produced by Pseudomonas sp. S-47 was similar to Xy1E of Pseudomonas putida with respect to substrate specificity for several catecholic compounds.