40 patients with degenerative joint diseases were treated with a new application form of naproxen (Proxen 500 film-coated tablets). The patients received one tablet daily in the evening for a period of 4 weeks. The therapeutic efficacy was demonstrated clinically on swelling of the joints, reduction of mobility, pressure pain, muscular stiffness and by improvement of pain symptoms: pain during day and night, pain at rest, movement pain. During therapy 75% of the cases showed marked improvement of the subjective and objective symptoms. The once daily application in the evening did not only influence favourable nocturnal and rest pain, but also reduced diurnal and movement pain significantly. In accordance with these findings 23 hours after application in the evening nearly constant serum levels of naproxen were found for the whole duration of treatment. The fast release of the active substance from the film-coated tablets leads to a rapid onset of the analgesic activity.