As many as 39 patients aged 16-70 years with rheumatoid arthritis (RA) lasting 3 months to 20 years were examined. The diagnostic titers of rheumatoid factor were discovered in 23 patients. The control group was made up of 26 healthy subjects (donors). The activity of IL-1 in supernatants of peripheral blood monocytes (PBM) was measured by bioassay resting on co-stimulation of mouse thymocytes; quantitative determination of tumor necrosis factor-alpha (TNF-alpha) was made by ELISA, PGE2 was determined by RIA. As compared to the controls, the RA patients manifested an increase of the production of IL-1 beta, TNF-alpha and PGE2 of PBM, which rose with the disease activity. The RA patients demonstrated direct correlations between the level of IL-1 beta, TNF-alpha and PGE2 in supernatants of PBM, whereas the donors showed up a negative correlation between IL-1 beta activity and PGE2.