Thymosin α 1 (Tα1), initially isolated from thymus, was characterized by Allan Goldstein in 1977. Since the beginning, our studies were aimed at evaluating its immunomodulating effects when used in combination with cytokines and chemotherapy. Combination therapies have now proved to be effective in inhibiting tumoral growth and in controlling infective diseases especially in the immunocompromised host. More recent studies showed that Tα1 molecule increased major histocompatibility complex (MHC) class-1 and Toll-like receptor expression as well as cytokine production, suggesting its immunoregulatory role. Overall these results led us to start pilot clinical trials on patients with hepatitis C and cancer.