The traditional clinical examination has been shown to have serious limitations in terms of its validity and reliability. The OSCE provides some answers to these limitations and has become very popular. Many variants on the original OSCE format now exist and much research has been done on various aspects of their use. Issues to be addressed relate to organization matters and to the quality of the assessment. This paper focuses particularly on the latter with respect to ways of ensuring content validity and achieving acceptable levels of reliability. A particular concern has been the demonstrable need for long examinations if high levels of reliability are to be achieved. Strategies for reducing the practical difficulties this raises are discussed. Standard setting methods for use with OSCEs are described.