Topoisomerases are enzymes that play imperative roles in replication, transcription, chromosome remodeling by managing the topology of DNA. To do so, topoisomerase generate either single-stranded cuts (type 1 topoisomerases) or double-stranded cuts (type II topoisomerase) in DNA by forming transient enzyme-DNA covalent intermediates termed topoisomerase cleavage complexes (TOPccs). Topoisomerases are also molecular targets of many approved and experimental anti-cancer agents, which stabilize TOPccs thereby interfering with DNA metabolisms. The proposed collection will provide protocols testing biochemical and cellular activities of topoisomerases as well as protocols assessing their inhibitors including assays to measure topoisomerase-mediated DNA cleavage, relaxation and decatenation, and drug-induced TOPcc trapping.