Pseudomonas sp. N.C.I.B. 9816 strain 11, when grown on salicylate in the presence of dibenzo[1,4]dioxan, accumulated cis-1,2-dihydroxy-1,2-dihydrodibenzo[1,4]dioxan and 2-hydroxydibenzo[1,4]dioxan in the culture medium. Each metabolite was isolated in crystalline form and identified by a variety of conventional chemical techniques. Crude cell extracts prepared from the parental strain grown with naphthalene oxidized cis-1,2-dihydroxy-1,2-dihydrodibenzo[1,4]dioxan under both aerobic and anaerobic conditions to 1,2-dihydroxydibenzo[1,4]dioxan. Further degradation of this metabolite was not detected.