The Paramyxoviridae form a large family of viruses containing many human and veterinary pathogens for which a need for antiviral treatment is emphasized, particularly following the recent emergence of new viruses. The viral RNA-dependent RNA polymerase constitutes an obvious target for antiviral compounds. An in vitro assay was developed that allows high throughput screening of compounds potentially inhibiting the Sendai virus RNA-dependent RNA polymerase. Screening relies on the detection of the Photinus pyralis luciferase produced in a transcription/translation coupled assay using a mini-replicon virus. It contains an internal control for possible adverse effects of the tested compounds on translation or on luciferase activity. It is estimated that the mini-replicon template produced in one fertilized egg is sufficient to run 5000-10,000 reactions. This assay constitutes a simple, sensitive and easily automated method to perform high throughput screening of Paramyxoviridae RNA-dependent RNA polymerase inhibitors.