This article presents a literature review on developments of membrane reactors for biological waste gas treatment as well as examples of applications to different compounds. The use of membranes combines selective separation of compounds from a waste gas stream followed by biological removal. Gas transport phenomena and different types of membranes used in biological waste gas treatment are discussed. So far, membrane-based biological waste gas treatment has only been tested on laboratory scale. If the long-term stability of these reactors can be demonstrated, membrane bioreactor technology can be useful in the treatment of gas streams containing poorly water-soluble pollutants and highly chlorinated hydrocarbons, which are difficult to treat with conventional methods for biological waste gas treatment. (c) 2007 Elsevier B.V. All rights reserved.