Polypeptides synthesized in Vero cells infected with African swine fever virus (ASFV) can be divided into early and late classes on the basis of their sensitivity to cytosine arabinoside. As ASFV does not inhibit cell protein synthesis until late in infection, immunoprecipitation was used to identify virus-specific polypeptides. Eighteen early and 15 late polypeptides were detected by polyacrylamide gel electrophoresis. Early polypeptides can be further divided into those which are transiently expressed at early times and the majority which are synthesized throughout infection. In vitro translation products of RNAs from infected cells at different stages of infection were compared with in vivo products after immunoprecipitation. A good correspondence was observed between the in vivo and in vitro patterns. All early RNAs translated in vitro were synthesized in the presence of cytosine arabinoside and cycloheximide and can therefore be classified as immediate early RNAs. Only two polypeptides transcribed from early RNA were not present among late RNA products. No evidence was obtained for a discrete class of delayed early RNAs.