Oxathiin carboxanilide (OC), NSC 615985, a compound originally synthesized as a potential fun de, was demonstrated to be highly active in preventing human immunodefriency virus (HIV)-induced cell ing and in inhibiting HIV reproduction. Virus-infected CD4+ lymphocytes were completely protected by 0.5 gsM OC, whereas no toxicity was observed at concentrations below 50 pM OC. Production of infectious virus, viral p24 antigen, and virion reverse transcriptase'were reduced by OC