An open study was carried out by 252 doctors throughout Portugal to assess the effectiveness and tolerability of oral glucosamine sulphate in the treatment of arthrosis. Patients received 1.5g daily in 3 divided doses over a mean period of 50±14 days. The results from 1,208 patients were analyzed and showed that the symptoms of pain at rest, on standing and on exercise and limited active and passive movements improved steadily through the treatment period. The improvement obtained lasted for a period of 6 to 12 weeks after the end of the treatment. Objective therapeutic efficacy was rated by the doctors as 'good' in 59% of patients and 'sufficient' in a further 36% (a total of 95%).