In recent years, both interferons and inductors of endogenous interferon production find increasing use in clinical practice. The latter agents are characterized by high antiviral and immunomodulatory activity in the absence of serious side effects, which makes it possible to prescribe long courses if necessary. One of the most frequently used interferon inductors is cycloferon. Diverse effects of cycloferon on biochemical and cellular cascades (including induction of alpha- and beta-interferon, inhibition ofproapoptotic factors such as tumor necrosis factor and interleukin 1-beta) suggest that it also takes active part in the regulation of apoptosis, one of the most important processes of cell activity that opens up new prospects for the therapeutic use of cycloferon.