Luciferase reporter gene assays have gained more importance because of their easy readout, high sensitivity and lack of environmental waste disposal problems. However, several obstacles remain that have prohibited a wider use and the implementation of this type of assay in high-throughput screening programs: (i) Measurements need to be carried out within an active enzyme reaction, and the assessment of such reactions are time-dependent; (ii) the signal produced has a "flash" type characteristic and therefore requires specialized equipment for measurement; and (iii) side-reactions can occur that interact with the signal readout of the assay in a non-reproducible way. These hurdles make an otherwise convenient assay principle troublesome for larger-scale screening use. We have attempted to overcome these problems by different means, leading to the development of LucLite, a stable signal homogeneous reagent system. This system allows use in a higher throughput screening capacity and enables the use of standard scintillation/luminescence instruments.