The regulation of dibenzothiophene (DBT) degrading activity of Rhodococcus erythropolis D-1 was examined. The enzymatic activity involved in DBT degradation of the strain D-1 was found in cell-free extracts of cells grown not only with DBT as a sole sulfur source but also with its analogs, thioxanthen-9-one and DBT sulfone. The activity was completely repressed in a medium with 0.5 mM sodium sulfate or 0.1 mM methanesulfonic acid even in the presence of DBT. The enzyme activity in the cell-free extracts of this strain was inhibited by a degradation product, 2-hydroxybiphenyl (2-HBP), and its analog, 2,2’-dihydroxybiphenyl (DHBP), but not by sodium sulfate and biphenyl. 2-HBP and DHBP also significantly inhibited the growth of this strain when it was cultivated in the medium supplemented with DBT as a sole source of sulfur.