In this report, aspects of epilepsy that differ in developing and in developed countries are reviewed. This is inevitably an incomplete and impressionistic survey, because data on many aspects in developing countries are scarce, and because it is difficult to generalise meaningfully about the enormous diversity of countries and populations that make up the developing world. Epidemiological studies of prevalence and incidence are reviewed with an emphasis on the problems inherent in work in this area in developing countries. Data concerning seizure type, aetiology, and severity of seizures in the Third World are contrasted with those from developed countries. Sociocultural aspects of epilepsy have been poorly studied, and yet are fundamental to effective medical management. The social effects of epilepsy and the local perceptions of cause and of treatment are discussed from work in Africa, Asia, and South America. The principles and success of treatment in the Third World may differ considerably in developing and developed countries. In the Third World, medical manpower is scarce, and epilepsy is managed essentially by primary care resources, without specialised investigations or personnel. The principles of drug therapy may not be understood by patients, and the supply of drugs is often erratic; and these are major reasons for poor compliance with treatment. World Health Organisation (WHO) initiatives have stressed the extensive use of paramedical personnel and of an essential drugs list, but this emphasis may be misdirected, and in practice neither proposal has achieved much success. The recommendation that phenobarbital be extensively used in the Third World, because of its cheapness and efficacy, is also of doubtful merit, as there are well-known and major drawbacks to the widespread use of this drug. Computations of treatment gap figures in three developing countries suggest that between 80-94% of patients with active epilepsy are not receiving anticonvulsant therapy, and cost is only one of a number of reasons for this. The key to improvements in medical treatment lie with a better understanding of the patients' cultural concepts of epilepsy and its treatment, improved drug supply and availability, and efforts to improve education amongst general practitioners and other primary care medical personnel.