Promoter deletion analysis is a useful tool for identifying important regulatory regions involved in transcriptional control of gene expression. In this approach, a series of promoter deletion fragments are fused to a reporter gene, such as chloramphenicol acetyltransferase or luciferase gene in a vector, and then transfected into cells for induction. Screening the expression level of the reporter gene using either a qualitative or a quantitative assay, allows to identify the regulatory regions of interest (e.g., cis-acting elements or enhancer) in the promoter.Luciferase genes have been widely used as reporter genes for their sensitivity and efficiency. Firefly and Renilla luciferases are two commonly used reporters, which oxidize different substrates to generate quantifiable luminescence. Therefore, the enzymatic activities of firefly and Renilla luciferases can be sequentially measured in a single sample by controlling reaction conditions. Here, we describe a dual-luciferase reporter assay, where the promoter of interest is fused to a firefly luciferase reporter and is co-transfected into cells with an internal control vector (pRL-CMV) to express Renilla luciferase. Both the Firefly and Renilla luciferases are measured using a dual-luciferase reporter assay system which improves experimental accuracy.