HTRF (H omogeneous T ime R esolved F luorescence) is the most frequently used generic assay technology to measure analytes in a homogenous format, which is the ideal platform used for drug target studies in high-throughput screening (HTS). This technology combines fluorescence resonance energy transfer technology (FRET) with time-resolved measurement (TR). In TR-FRET assays, a signal is generated through fluorescent resonance energy transfer between a donor and an acceptor molecule when in close proximity to each other. Buffer and media interference is dramatically reduced by dual-wavelength detection, and the final signal is proportional to the extent of product formation. The HTRF assay is usually sensitive and robust that can be miniaturized into the 384 and 1536-well plate formats. This assay technology has been applied to many antibody-based assays including GPCR signaling (cAMP and IP-One), kinases, cytokines and biomarkers, bioprocess (antibody and protein production), as well as the assays for protein-protein, proteinpeptide, and protein-DNA/RNA interactions.