The modifications in plasma, erythrocyte and urine zinc and copper concentrations induced by chronic or acute corticotherapy were studied in patients suffering from rheumatoid arthritis and the results compared with those from controls. Patients not treated with corticosteroids had low plasma zinc and high plasma copper, which significantly correlated with inflammatory parameters (erythrocyte sedimentation rate and C-reactive protein); no change was observed in erythrocyte and urine zinc and copper. Oral long-term treatment with corticosteroids (less than 10 mg prednisolone/day) was associated with a further decrease in plasma zinc only in patients with moderate inflammation. Changes induced by such a treatment were less intense than those due to severe inflammation. The administration of intravenous high doses (1 g methylprednisolone/day) resulted in a rapid decrease in plasma zinc with a return to baseline levels two days after withdrawal. The modification was associated with a sustained increase in urine zinc and copper without changes in diuresis.