In the selection of a muffler for the reduction of the exhaust noise of an internal combustion engine the acoustical problems are only one of many. Attention must also be given to problems of space availability and configuration. It is important that the best material for the purpose is chosen. Equally important is the most economic utilization of this material both from the standpoint of original cost and availability as well as the practical aspect of ease of production. Not only basic acoustical design but some of the problems of fabrication and attachment are discussed. Special mufflers, including catalytic afterburners, are discussed in detail.