Congo Basin hunter-gatherers have used cannabis for nearly two centuries, yet ethnographic descriptions of its use are rare or contradictory. We present the results of two projects investigating cannabis use among Congo Basin hunter-gatherers. The first study, conducted in the 1970s, was a survey of cannabis use in three populations: Efe archers, Mbuti net-hunters, and Aka net-hunters. The second study, conducted in 2011, was an in-depth biocultural study of cannabis use among one of these groups, the Aka. Methods varied between the studies, but the integration of results from both studies provide insights into: a) common features of Congo Basin hunter-gatherer cannabis use across time and space; b) cross-cultural and intracultural diversity in use; and, c) factors influencing changes in use over time. Compared to typical cannabis research populations in Western, developed countries, cannabis use among Congo Basin hunter-gatherers involves extensive sharing, such as communal smoking, absence of gender or age proscriptions, perceived performance enhancing effects, and labor-for-cannabis exchanges with neighboring villagers. Cannabis was sometimes the first or the only plant that Congo hunter-gatherers domesticated. Consistent with cross-national studies of cannabis use, Congo Basin hunter-gatherer cannabis users were typically male, often adolescent or young adult, and (among Aka in 2011) had less material wealth than non-users. Aka cannabis users also had fewer intestinal parasites. Finally, cannabis use varied across time and space both within and between the three groups in ways that reflect differences in the demographic, cultural, and historical features of the populations, especially degree of sedentarization and market integration.