A series of "viologen" derivatives (4,4'-bipyridinium salts) carrying between 1 and 90 charges per molecule have been prepared and investigated for their activity against human immunodeficiency virus (HIV), herpes simplex virus (HSV), vesicular stomatitis, Punta Toro virus, Sindbis virus, Reovirus, and respiratory syncytial viruses. In general, most of the compounds showed good activities against HIV-1 (strain III(B)). In particular, compound 36 exhibited the highest in vitro activity and selectivity index against HIV-1 (strain III(B)) (EC(50) = 0.26 +/- 0.08 microM, SI = 75.7) in MT-4 cells. The results imply that the antiviral activity requires an optimal number and distance of the positive charges.