The pGL3 Luciferase Reporter Vectors provide a basis for the quantitative analysis of factors that potentially regulate mammalian gene expression. These may be cis- or trans-acting factors. The backbone of the pGL2 Luciferase Reporter Vectors was redesigned for the pGL3 Vectors for increased expression, with a modified coding region for firefly (Photinus pyralis) luciferase that has been optimized for monitoring transcriptional activity in transfected eukaryotic cells. The assay of this genetic reporter is rapid, sensitive and quantitative. In addition, the Luciferase Reporter Vectors contain numerous features aiding in the structural characterization of the putative regulatory sequences under investigation. For the most advanced reporter vectors and widest selection of features, please see the pGL4 series of vectors.