Marker-assisted breeding could have a major impact in relieving productivity constraints that cannot as easily or rapidly be relieved by conventional breeding alone. This paper estimates the benefits of using marker-assisted breeding, as compared to conventional breeding alone, in developing cassava varieties resistant to cassava mosaic disease, green mite, whitefly and post-harvest physiological deterioration in Nigeria, Ghana and Uganda. Marker-assisted breeding is estimated to save at least four years in the breeding cycle for varieties resistant to the pests and to result in incremental net benefits over 25 years in the range of $34 to $800 million depending on the country, the particular constraint and various assumptions. Benefits may reach as high as $3 billion for resistance to post-harvest physiological deterioration, as conventional breeding is not projected to solve the problem within a reasonable time frame.