Correct diagnosis of restless legs syndrome (RLS) is essential to patient care and treatment. Diagnosis is most often clinical and based on diagnostic criteria: the need to move the legs accompanied to varying degrees by unpleasant sensations, predominantly during the evening and improved by movement. In rare cases, clinical examination is insufficient and a polysomnography is necessary. Once a positive diagnosis has been made, a neurological examination and an assessment of iron status are required. The severity of the RLS must be evaluated to determine whether a specific treatment is necessary. Before treatment, it is essential to ensure that a definite diagnosis of RLS has been made and the phenotype characterised. This enables a personal treatment plan and limits the risk of augmentation syndrome.