Medical training has traditionally depended on patient contact. However, changes in healthcare delivery coupled with concerns about lack of objectivity or standardization of clinical examinations lead to the introduction of the 'simulated patient' (SP). SPs are now used widely for teaching and assessment purposes. SPs are usually, but not necessarily, lay people who are trained to portray a patient with a specific condition in a realistic way, sometimes in a standardized way (where they give a consistent presentation which does not vary from student to student). SPs can be used for teaching and assessment of consultation and clinical/physical examination skills, in simulated teaching environments or in situ. All SPs play roles but SPs have also been used successfully to give feedback and evaluate student performance. Clearly, given this potential level of involvement in medical training, it is critical to recruit, train and use SPs appropriately. We have provided a detailed overview on how to do so, for both teaching and assessment purposes. The contents include: how to monitor and assess SP performance, both in terms of validity and reliability, and in terms of the impact on the SP; and an overview of the methods, staff costs and routine expenses required for recruiting, administrating and training an SP bank, and finally, we provide some intercultural comparisons, a 'snapshot' of the use of SPs in medical education across Europe and Asia, and briefly discuss some of the areas of SP use which require further research.