The clinical efficacy of a herbomineral formulation containing roots of Withania somnifera, the stem of Boswellia serrata, rhizomes of Curcuma longa and a zinc complex (Articulin-F), was evaluated in a randomized, double-blind, placebo controlled, cross-over study in patients with osteoarthritis. After a one-month single blind run-in period, 42 patients with osteoarthritis were randomly allocated to receive either a drug treatment or a matching placebo for a period of three months. After a 15-day wash-out period the patients were transferred to the other treatment for a further period of three months. Clinical efficacy was evaluated every fortnight on the basis of severity of pain, morning stiffness, Ritchie articular index, joint score, disability score and grip strength. Other parameters like erythrocyte sedimentation rate and radiological examination were carried out on a monthly basis. Treatment with the herbomineral formulation produced a significant drop in severity of pain (P less than 0.001) and disability score (P less than 0.05). Radiological assessment, however, did not show any significant changes in both the groups. Side effects observed with this formulation did not necessitate withdrawal of treatment.