We studied the influence of chrysotherapy on lymphocytes, B-cells, T-cells, and T-lymphocyte subpopulations in 9 rheumatoid-factor-positive female patients with rheumatoid arthritis (RA). After chrysotherapy, the white blood cell count decreased within 1 month; the percentage of lymphocytes, T-cells, and B-cells did not change significantly, nor did the proportion of helper cells as determined by reactivity with monoclonal antibody OKT4. In contrast, the percentage of suppressor T-cells reactive with OKT8 was significantly decreased (p less than 0.05) after 6 months. As a consequence, the helper/suppressor ratio, which was significantly higher than in age- and sex-matched controls (p less than 0.02), showed an even more pronounced deviation from normal values than before therapy. The implications of these findings in regard to a possible immunological mechanism of action of gold and the significance of the disturbance of the "immunoregulatory balance" between helper and suppressor mechanisms for the pathogenesis of RA are discussed.