There are only a limited number of effective, non-toxic antiviral drugs for clinical use, whereas there is a great need for such drugs. Especially for the treatment of patients infected with the human immuno-deficiency virus (HIV) anti-HIV drugs are required. At the same time viral infections secondary to AIDS cannot yet be treated effectively. An increasing problem is the development of virus strains resistant to the available drugs. At this moment a great effort is made in the research for new antiviral drugs. In this article the available antiviral drugs are reviewed. Their antiviral properties, mechanism of action, clinical use, pharmacokinetic properties and side-effects are discussed. Some attention is paid to the future directions in the search for new anti-HIV drugs.