AbstractThe complexity of magnetic confinement machines has been a matter of concern in developing fusion power plants as electricity generating stations because it might reduce plant availability. A comprehensive reliability and availability (R&A) programme to determine the availability of a next step fusion machine was performed during definition and conceptual design of the Next European Torus. In addition to giving an overview of the expected contributions to unavailability of the various components, this activity identified the basic approach to be taken to specify and to achieve necessary improvements. This paper, after giving some basic definitions, describes the essentials of the R&A programme, its results, and the guidelines derived for further work towards a sufficiently reliable fusion plant. These guidelines refer to improvement of the reliability database and the quality assurance to be performed at the design stage of a next step machine.