The European Restless Legs Syndrome (RLS) Study Group (EURLSSG) is an association of European RLS experts who are actively involved in RLS research. A major aim of the Study Group is the development and continuous improvement of standards for diagnosis and treatment of RLS. Several members developed study designs and evaluation methods in investigator-initiated trials early in the 1990s, and all members have since contributed to many pivotal and nonpivotal drug trials for the treatment of RLS. The recommendations on clinical investigations of pharmacological treatment of RLS patients summarize the group's expertise and knowledge acquired through clinical trials. The recommendations primarily address how to plan and conduct confirmatory, randomized clinical studies in patients with idiopathic RLS. Advice is presented for the diagnosis of RLS and clinical and polysomnographic inclusion and exclusion criteria. Primary and secondary endpoints for an evaluation of efficacy are based on a critical description of validated methods for both short- and long-term trials, also in special populations (children, pregnant women, elderly patients). The recommendations include the assessment of augmentation. Finally, general issues including the evaluation of safety and tolerability, as well as specific neurological and cardiovascular risks and sleep attacks/daytime somnolence, are discussed. The aim of these recommendations is to support research groups or pharmaceutical companies in the design of optimized study protocols.