Although the etiology of rheumatoid arthritis (RA) is unknown, there is solid evidence that immunological factors play a pivotal role in its pathogenesis. It seems that a hyporeactivity of local (intraarticular) T-suppressor cells would permit an excessive immune response that ultimately leads to the classical symptoms and signs of inflammation and cartilage damage. Thymopentin is a synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr) which represents the active biologic site (sequence 32-36) of the native thymic hormone thymopoietin, containing 49 amino acids. Thymopoietin and thymopentin have been shown to possess immuno-normalizing properties in a number of animal model systems. Low concentrations of the hormone characteristically stimulate the OKT4-positive cells, whereas higher concentrations additionally induce stimulation of OKT8-positive cells. This report summarizes the clinical experience collected by Italian investigators, and discusses the results with a view to previously published papers.