The increasing role of the immune system in controlling the chronic inflammation and tumor growth indicates that a suitable therapeutical strategy is its modulation by new compounds able to enhance immunogenicity of relevant antigens and to revert effector T cell responses (usually Th2 and Th17) in a more protective one (Th1). Recently the family Toll-like receptors (TLRs) has been identified as the major group of sensors for microbial components. TLRs agonists, enhancing both innate and adaptive immunity, are now largely studied for their intrinsic and valid adjuvant activity. In this view, ligands of TLRs (expecially endosomic TLRs) represent a promising class of compounds able to redirect inflammation or to improve anti-tumor response, and, therefore, to be used as adjuvants in allergy vaccines or anti-cancer immunotherapy. In particular, TLR7 agonists are able to simultaneously stimulate different cells of the immune system, leading to a large number of Th1 effector cells in pathological sites.