We examined the use of Kratom (Mitragyna sp.), a dietary supplement with mu-opioid agonist activity, by members of a cybercommunity who self-treat chronic pain with opioid analgesics from Internet pharmacies. Within one year, an increase in the number of mentions on Drugbuyers.com, a Web site that facilitates the online purchase of opioid analgesics, suggested that members began managing opioid withdrawal with Kratom. This study demonstrates the rapidity with which information on psychoactive substances disseminates through online communities and suggests that online surveillance may be important to the generation of effective opioid analgesic abuse prevention strategies.