The results of analyses of fowl plague virus-specific RNA and protein synthesis in infected chick embryo fibroblasts incubated in amantadine hydrochloride are reported. They indicate that provided amantadine is present from the time of virus addition no expression of the virus genome occurs and that the synthesis of even the first detectable transcripts catalysed by the polymerase of the infecting virus particles is prevented. In agreement with previous reports it is concluded that amantadine prevents an unknown event which occurs immediately following virus infection.