Online drug markets located on the so-called darknet provide researchers, policy makers and practitioners with unprecedented insights. After explaining the structure and function of drug cryptomarkets, this presentation details the range of information available from these marketplaces and how researchers go about its collection. Taking illustrations from the fast-growing research literature, the presentation identifies how cryptomarket data can inform our understanding not only about this new platform for illicit drug trading, but about much else besides. The drug monitoring capacities of cryptomarket data also function as a window into global patterns of illicit drug use and diffusion; international drug trafficking. Because drug cryptomarkets generate ‘big data’ about dated transactions differentiated by drug type, price and quantity, policy analysts gain previously unavailable insights into changing trends in the illicit drug trade that can be precisely pinpointed in time, and so more effectively inform policy evaluations.