The Renilla Luciferase Assay System is designed to provide a fast and sensitive method of detecting sea pansy (Renilla reniformis) luciferase. This system is a convenient alternative to firefly (Photinus pyralis) reporter systems and is designed to yield reliable, linear results for a concentration range over seven orders of magnitude. The Renilla Luciferase Assay System has been formulated with a proprietary composition that significantly reduces the coelenterazine autoluminescence commonly seen with other reagents. The result is an assay system that is more sensitive than published methods by several orders of magnitude. This sensitivity is comparable to that seen with the firefly Luciferase Assay System. The Renilla Luciferase Assay System enables measurement of Renilla luciferase activity using either the wildtype or new synthetic Renilla luciferase as a primary reporter to study transcriptional regulation or as a co-reporter for normalization of experimental variations such as differences in transfection efficiencies.