The streptovaricins are one of five members of a group of antibiotics collectively referred to as ansamycins. The review of current knowledge of the chemistry and biological activity of the streptovaricins will develop the interesting speculation that this class of antibiotics may possess a broader antiviral spectrum. The pharmacology of a partially purified mixture of streptovaricins B and C plus about 30% inactive material was examined in dogs by Wallach and Wagner, as well as with a filter disk bioassay against Sarcina lutea. In view of the wide spectrum of bacteria inhibited in vitro, the good correlation between in vitro and in vivo activity, and the low toxicities in vivo, the lack of clinical investigations with the streptovaricins is puzzling. The structure-activity results do show that antileukovirus activity is unrelated to antibacterial activity, in which streptovaricins A, B, and C are active.