BacMam viruses are modified baculoviruses that contain mammalian expression cassettes for viral gene delivery and transient expression in mammalian cells. They are easily, inexpensively, and rapidly generated and provide a versatile solution for G protein-coupled receptor (GPCR) cell-based assay development. Using BacMam technology, target gene expression levels are easily controlled and simultaneous delivery of multiple genes is possible, for example, coexpression of a receptor and a G protein or a reporter gene. BacMam viruses are compatible with the GPCR cell-based assay formats typically used in high-throughput screening and provide an unparalleled level of experimental flexibility that is simply not possible when using stable recombinant cell lines.