In 1994, a combined committee of the World Health Organization and the International League of Associations for Rheumatology published recommendations for clinical trials for 2 classes of agents for treatment of osteoarthritis (OA) that relieved symptoms but differed in their onset and duration of response, and a third class of agents that may alter the disease process. Recently, the European Group for the Respect of Ethics and Excellence in Science made recommendations for methods to be used in the registration of drugs for OA. Following the 2nd international meeting of the Osteoarthritis Research Society in December 1994, a task force was convened to develop recommendations for the design and conduct of clinical trials in patients with OA. The Task Force had several meetings over the past 16 months, resulting in the preliminary recommendations summarized here.