With completion of the sequencing of the human and mouse genomes, the primary sequences of close to 400 non-olfactory G protein-coupled receptors (GPCRs) have been determined. There are intensive efforts within the pharmaceutical industry to discover and develop new therapeutic agents acting via GPCRs. In addition, there is a concerted effort to identify potential new drug targets from the remaining 150+orphan GPCRs through the identification of their ligands. Access to functionally expressed recombinant receptors underpins both of these key drug discovery activities. Typically, GPCR drug discovery screening activities are carried out using mammalian cell lines stably expressing the target of interest. The influx of new receptor sequences originating from genomic sequencing efforts has caused a shift toward wider applications of transient rather than stable expression systems, especially in support of assays for orphan receptor ligand screening. Recombinant baculoviruses in which the polyhedrin promoter has been replaced with a mammalian promoter, termed BacMam viruses, were originally designed as potential new gene therapy delivery vehicles. This same technology offers numerous advantages as a transient expression system in the assay of membrane-expressed drug targets, including GPCRs. Data presented show that BacMam can be used rapidly to generate robust and pharmacologically authentic GPCR assays in several formats, with the potential to transform drug discovery screening processes for this gene family.