"This paper describes the dramatic cassava transformation that has taken place in Nigeria and Ghana over the past 50 years. From a rural subsistence crop, cassava has become a major cash crop sold in urban markets, a source of livestock feed, industrial starch and urban convenience foods. This paper documents the key factors driving the cassava transformation in Nigeria and Ghana. Differences in timing, promotional efforts and performance provide an instructive contrast which helps to identify key factors necessary for stimulating significant growth in cassava production elsewhere....In Nigeria and Ghana, four key factors are driving the cassava transformation. First, the IITA's new high-yielding Tropical Manioc Selection (TMS) varieties boosted cassava yield by 40 percent without fertilizer application. Second, high consumer demand for cassava by rural and urban households fueled the producer incentive to plant more land to cassava. Third, the use of the mechanical grater to prepare gari released labor, especially female labor, from processing for planting more cassava. Fourth, the Africa-wide biological control program averted the devastating cassava mealybug epidemic. -- Authors' Abstract"