The paper is primarily from an individual shipowner's viewpoint. The first part of the paper considers the likely trends with regard to main propulsion systems arising from that viewpoint. It takes into account the emphasis on reliability and safety, pollution problems, and the combination of capital and operating costs of the system. Consideration is given to the various fuels used with prices and price trends. This is related to an analysis of the various types of propulsion systems presently available including gas turbine and nuclear power systems. In the second part of the paper, the individual views are compared with those derived from a statistical investigation of trends in machinery installations related to ship types and sizes based on published data. The conclusions drawn from the two approaches are in close agreement that in the 1980s the most widely used propulsion systems will be the slow speed diesel and the geared steam turbine with the main contenders being the medium speed diesel engine and the gas turbine. Nuclear propulsion is ruled out for this period because of pollution hazards and high capital costs.