The review summarizes current knowledge about the different metabolic pathways of PCBs which occur mainly in Gram-negative bacteria. The complete degradation of PBCs includes the following metabolic pathways: "upper" pathway - degradation of PCB to chlorobenzoates and pentadiene acids, "lower" pathway - degradation of chlorobenzoates, degradation of pentadiene acids. Examples of different metabolic routes in various bacterial strains are given.