The extent of soil erosion, particularly in developing countries, is such that serious constraints to economic growth will occur in the medium and long term. This chapter aims to assess the extent of erosion in developing countries. It presents the existing empirical evidence on erosion at the country level, the extent of erosion effects at the farm level, the impact of erosion on downstream economic activities, sedimentation rates at major dams of the world, flood damages and water quality changes and global estimates of erosion rates in developing countries. Differences in soil and climate have produced an almost infinite variety of cropping systems in developing countries. Climate determines to a large extent the type of soil and vegetation in a given region and thus influences the utilization of the land. Climatic and geological factors make the region particularly susceptible to erosion. The effects of soil erosion are also similar across countries.