This paper identifies and elucidates what it calls the Malthus Effect from two perspectives: a genealogical-theoretical one and an empirical-diagnostic one. The first concerns its implications for Michel Foucault's genealogy and conceptions of modern governmentality. The second suggests that Malthusian concerns have an enduring presence in recent and contemporary politics. In them we find a government of life that tethers the question of poverty to that of population, as both a national and international concern, links biopolitics to questions of national security and is a key source of the modern environmental movement. It remains present in areas such as welfare reform and immigration policy, notions of sustainability and in the global public health and environmental movements. It takes the form of a genopolitics, a politics of the reproductive capacity of human populations and the human species.