A transient expression assay for fowlpox virus (FPV) was developed to assess the feasibility of using heterologous promoters in FPV and to qualitatively determine relative promoter strength. A transient expression system for FPV has not been reported, and various methods used for transient expression in vaccinia-virus-infected cells produced negative results when used with FPV. Here a successful method for transient expression of E. coli beta-galactosidase in FPV-infected chick embryo fibroblasts is reported. This transient expression assay has been developed to qualitatively assess promoter recognition and gene expression by FPV. It should also prove useful in the identification of promoters from the FPV genomic library and in testing the accuracy of chimeric promoter-gene constructs.