The blood concentrations of calcium, magnesium, copper, zinc, lead and chromium were measured in patients with rheumatoid arthritis and in a "normal" control group. The values of hemoglobin and the effect of some drugs on the metals studied were also estimated. In metal analyses the atomic absorption spectrophotometric technique was used. The mean concentration of copper in the blood of patients with rheumatoid arthritis was significantly higher than in the control group. This was not true in females taking conteceptive drugs that cause elevated serum copper concentrations. Chromium concentrations were significantly lower in patients with rheumatoid arthritis. The mean concentrations of zinc was higher in rheumatoid females than in female controls. The concentrations of calcium, magnesium and lead were not found to be different in patients with rheumatoid arthritis from those in the control group.