A rapid expansion of our knowledge of drugs that intervene with human immunodeficiency virus (HIV) infection has taken place. This review covers known and potential anti-HIV targets, including receptor blocking agents, membrane stabilisers, reverse transcriptase inhibitors and chain terminators, RNases, agents altering activation, assembly, budding or regulation of transcription and translation, post-transcriptional modifications and other areas. Important or promising agents, such as zidovudine (ZVD; azidothymidine, AZT), dideoxycytidine, dideoxyinosine, foscarnet, interferons, imuthiol, isoprinosine and others that are either on the market or in advanced clinical trials are emphasised. Four years after the discovery of the aetiological agent, the first drug, zidovudine, has been registered. Many questions about this drug remain, however, owing to the haste with which it was developed. An unprecedented number of other compounds are under evaluation, making it difficult to assess the relative merits of the different compounds and thus set priorities for their development. The point has been reached where a better economical and intellectual framework is necessary so that researchers and physicians are not overwhelmed by the difficulties of conducting clinical trials during the epidemic and have a reasonable chance of keeping up with laboratory developments.