Brivudin, (()-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) can be considered the gold standard for the treatment of varicella-zoster virus (VZV) infections, such as herpes zoster (shingles). It is available for clinical use in most European countries (except for the UK) and over the whole world (except for the US and Canada). Besides VZV its activity spectrum also includes various other herpesviruses, such as herpes simplex virus type 1 (HSV-1). Its activity against VZV and HSV-1 depends on phosphorylation by the virus-encoded thymidine kinase (TK). In its active form (BVDU TP or BVDU 5'-triphosphate), it can act as both substrate and inhibitor of the viral (i.e., HSV-1) DNA polymerase. It has proven to be effective against herpes zoster, including post-herpetic neuralgia (PHN). It is contra-indicated in patients concomitantly treated by 5-fluorouracil (FU), since its degradation product, ()-5-(2-bromovinyl)uracil, is inhibitory to the catabolism of FU, which may enhance the toxicity of the latter. A new compound, the bicyclic nucleoside analogue (BCNA) Cf-1743, has been described, which is a more potent inhibitor of VZV replication than BVDU and which does not interfere with the catabolism of FU. It is applicable orally, as its 5'-valine ester FV-100 (Fermavir), but has not (yet) been marketed for clinical use.