Cellular defense pathways are not the only mechanisms restricting viral replication. The competition between closely related virus genomes, known as ��homologous interference��, or ��superinfection exclusion�� remains incompletely understood. In cultured cells, Didanosine Sindbis genomes originating from infectious particles or from injection can exclude each other��s replication. Moreover, even closely related alphaviruses exhibit ��superinfection exclusion��. These studies suggested that initial infection with a first virus leads to production of only few orientation ��antigenomes��. In addition, cleavage of the replicase polyprotein by a Pramipexole trans-acting protease, leads to a loss of replication activity, while transcription of ORF2 from the internal promoter remains unaffected. As a consequence, while ORF1 of the superinfected virus genome is still translated, its RdRP can no longer produce a ��subgenomic RNA�� containing the superinfecting ORF2. However, certain aspects of ��superinfection exclusion�� remain incompletely understood. For instance, it is unclear whether the exclusion mechanism selects only a single genome or a small number of genomes for replication, and the extent to which host proteins are required for the exclusion process to be effective remains unknown. We have developed a multi-purpose Drosophila toolkit of inducible, transgenic Sindbis replicons for the rapid visualization and quantitative analysis of virus replication in vivo with high spatiotemporal precision. We have generated Luciferase expressing replicons that can be used as an alternative to real-time qPCR for the quantification of viral replication in many different tissues, as well as in different mutant backgrounds. We have also generated replication-deficient replicons harboring large deletions spanning virus ORF1, which encodes the viral replicase. With such deficient replicons carrying either a fluorescent protein or Luciferase we can genetically separate both RdRP-production and transcription of ORF2 from ��subgenomic RNA��, leading to a binary system of trans-complementing replicons. Furthermore, intact, replication-competent transgenic replicons expressing different fluorescent markers can be used to simultaneously visualize replication of competing replicon populations in vivo.