Two drug formulations of povidone-iodine (PVP-I)--an aqueous PVP-I solution (Betaisodona) and a liposomal PVP-I formulation--were tested for their virucidal activity and cytotoxicity in cell culture. As to the virudical activity against influenza A virus, herpes simplex virus type 1, adenovirus type 8 and human rhinovirus type 14, the liposomal formulation of PVP-I proved to be approximately as active as the aqueous one. Half maximum cytotoxic PVP-I concentrations were 0.01-0.07% for aqueous PVP-I and 0.03-0.27% for the liposomal PVP-I formulation (XTT reduction assay EZ4U). The detection of lactate dehydrogenase (LDH) release, DNA fragmentation (ELISA) and DNA strand breakage (TUNEL assay) after 24 h exposure of human embryonic lung fibroblasts to PVP-I revealed that necrosis predominates in cells treated with aqueous 0.08-0.32% PVP-I solutions, whereas apoptosis was the predominant type of cell death in cells treated with equivalent concentrations of liposomal PVP-I formulation. The favorable virucidal efficiency together with the preferred apoptotic route of cell death makes the liposomal PVP-I formulation a promising candidate for topical use in prevention and treatment of infections of the eye and the upper respiratory tract.