The authors have studied the synthesis of interleukin 1 by articular and circulating macrophages and the effect of two types of interferon alpha (IF) on this synthesis in 20 patients with untreated rheumatoid arthritis (RA). The articular and especially systemic interleukin levels in the RA patients are significantly higher than those of the test subjects. Interferon modifies in a very different way the production of interleukin 1 in the patients and in the test subjects. This is linked with the in vitro experimental conditions as well as the increase in the IL1 levels in the patients. The authors discuss the perspective therapeutics offered by this modulation of interleukin production by interferon.