Investigation of an epidemic of more than 1000 cases of spastic paraparesis in a drought-striken cassava staple area of Mozambique strongly suggests an association between this disease (called mantakassa), chronic cyanide intoxication, and cassava consumption. In previous reports of neurological disease with similar associations, the disease affected an older age group with usually a gradual onset, and the predominant clinical feature was an ataxic neuropathy. In mantakassa the onset was acute, and mostly women of reproductive age and children were affected. Serum thiocyanate levels in these patients were much higher than previously reported; while spastic paraparesis of unknown etiology occurs in many tropical countries, it has not previously been linked with raised thiocyanate levels. The present evidence linking cassava consumption to the disease is circumstantial, and dietary deficiency is also probably involved. Cassava is an important food crop and a major source of energy for people in many parts of the world. In these areas, when there is a shortage of food production, e.g., during a drought, the inhabitants may be exposed to the risk of dietary cyanide intoxication. Further research is needed on the causes of mantakassa so that a repetition of this disaster could be prevented.