The diagnosis of RLS has been undergoing a gradual evolution, but remains anchored in a 'gold standard' of an expert clinical interview. The most recent standards emphasize the presence of one main symptom - The urge to move - and three key modulators: rest, activity, and time of day. Beyond establishing these key features, the major diagnostic challenge is to eliminate mimics. Objective test scan be helpful in doubtful cases, but have not become accepted as diagnostic criteria. Improving technology may make them more useful in the future. Meanwhile, the diagnosis of RLS outside of the expert clinical interview and as applied to diverse populations is less clearly understood. Some studies suggest that those affected with RLS in the community may differ at least in severity from those who have become patients. The non-patient individual with RLS may present significant and greater diagnostic challenges than patients. Work remains to be done to further validate useful epidemiological and screening instruments for this population. Ongoing discoveries in the pathophysiology and genetics of RLS may contribute to greater diagnostic accuracy, additional diagnostic instruments, and new assessment measures in the future. © 2004 Published by Elsevier B.V.