Telomerase is the ribonucleoprotein enzyme that catalyzes the processive addition of the telomeric DNA repeat 5'-TTAGGG-3' onto chromosome ends. In addition to its fascinating biochemical and enzymatic properties, clinical interest in telomerase stems from its dysregulated expression in similar to 90% of human cancers, representing a broad spectrum of diseases. Exploiting telomerase as a therapeutic target and hence identifying and/or evaluating potential inhibitors requires quantitative measurement of its activity. This article presents procedures for measuring multiple aspects of telomerase enzymology that are relevant to both fundamental biochemistry and drug discovery: direct activity assays, DNA binding affinity, DNA dissociation, and cell-based over-expression of the active enzyme complex. (C) 2016 Elsevier Inc. All rights reserved.