"Despite the fact that sub-Saharan Africa in 2012 contains much of the world’s unutilized and underutilized arable land, a significant and growing share of Africa’s farm households live in densely populated areas. Based on two alternative spatial databases capable of estimating populations at the level of one square kilometer and distinguishing between arable and non-arable land, we find that in at least four of the 10 countries analyzed, 25% of the rural population resides in areas exceeding 500 persons per square kilometer, estimated by secondary sources as an indicative maximum carrying capacity for areas of rain-fed agriculture in the region. The apparent paradox of a large proportion of Africa’s rural population living in densely populated conditions amidst a situation of massive unutilized land is resolved when the unit of observation moves from land units to people. A review of nationally representative farm surveys shows a tendency of (1) declining mean farm size over time within densely populated smallholder farming areas; (2) great disparities in landholding size within smallholder farming areas, leading to highly concentrated and skewed patterns of farm production and marketed surplus; (3) half or more of rural farm households are either buyers of grain or go hungry because they are too poor to afford to buy food; most households in this category control less than one hectare of land; and (4) a high proportion of farmers in densely populated areas perceive that it is not possible for them to acquire more land through customary land allocation procedures, even in areas where a significant portion of land appears to be unutilized. Ironically, there has been little recognition of the potential challenges associated with increasingly densely populated and land-constrained areas of rural Africa, despite the fact that a sizeable and increasing share of its rural population live in such areas. Inadequate access to land and inability to exploit available unutilized land are issues that almost never feature in national development plans or poverty reduction strategies. In fact, especially since the rise of world food prices after the mid-2000s, many African governments have made concerted efforts to transfer land out of customary tenure (under the control of traditional authorities) to the state or to private individuals who, it is argued, can more effectively exploit the productive potential of the land to meet national food security objectives. Such efforts have nurtured the growth of a relatively well-capitalized class of 'emergent' African farmers. The growing focus on how best to exploit unutilized land in Africa has arguably diverted attention from the more central and enduring challenge of implementing agricultural development strategies that effectively address the continent’s massive rural poverty and food insecurity problems, which require recognizing the growing land constraints faced by much of its still agrarian-based population. The final section of the paper considers research and policy options for addressing these problems."