It is important for the oil industry to anticipate the restriction of the dumping of oil-containing waste at sea. This paper describes research into the use of micro-organisms to disperse and biodegrade the oil component of cuttings and spent drilling muds before discharge. Bacteria using diesel fuel have been isolated from natural sources. Conditions appropriate to the treatment of oil based muds have been developed using an air lift fermenter. Already selected organisms can degrade in less than two days 100% of many alkanes, 63% of pristane and 46% of phytane originally in the mud. Work is continuing to optimize physical and chemical conditions.