What role has intense population pressure played (and continues to play) in ancient and contemporary transformations in Burundian agriculture? A considerable disincentive to development and source of imbalance for some, an engine of agricultural growth for others: does this age-old debate still make sense in the present context? Based on an extensive study of agrarian dynamics, the reconstruction of the different agrarian systems that have been in place in Burundi, and an investigation of the phases of major transformations that have enabled the passage of one system to another, the author ventures a rereading of the most commonly cited interpretations of Malthus and Boserup, and proposes a new approach to this fundamental question.