Sweet potato is an important staple crop in East Africa, where it provides vital food for resourcepoor farmers. It is also gaining ground among urban populations, and new orange-fleshed varieties of sweet potato offer hope against crippling and widespread vitamin A deficiencies. Sweet potato virus disease (SPVD) is the most damaging disease affecting this crop in Africa, sometimes causing huge losses. Plants with SPVD yield 60-98 percent less than uninfected plants. Using a combination of good farming practices and resistant varieties, farmers can control virus diseases and ensure abundant harvests. This booklet outlines the importance of sweet potatoes in Africa, the effects of viruses, and how to combat virus diseases.