Inosine pranobex (inosine dimepranol acedoben, isoprinosine) (Inos) is an immunomodulatory and antiviral drug used in some viral infections, especially in patients with weakened immunity. In the present study, eff ects of Inos on the production of cytokines a ributable to Th1 (IL-2, IFN-g, and TNF-a) or Th2 cells (IL-4, IL-5, and IL-10) were tested in human peripheral blood lymphocyte cultures stimulated with phytohemagglutinin (PHA). Inos enhanced TNF-a secretion signifi cantly (in short-term -24-hour, and prolonged term -72-hour cultures) and . Surprisingly, production of IL-10 by PHA-stimulated lymphocytes was suppressed by Inos in a dose-depen dent manner in both 24-hour and 72-hour cultures. These results shed some light on immunomodulatory properties of Inos and suggest applicability of this agent in patients with a depressed function of the immune system.