The two most controversial aspects of the management of sickle-cell disease are first, the treatment of the painful, vasoocclusive crisis and second, the value of community screening programmes. The controversy over treatment of the painful crisis has followed the promotion of urea as a clinically effective anti-sickling agent (Nalbandian, Shultz, Lusher, Anderson, and Henry, 1971; McCurdy and Mahmood, 1971) against a long background history of failure to evaluate potential anti-sickling agents by controlled clinical trial. The controversy over community screening has been exacerbated by the passage, in 1972, of the United States Congress National Sickle Cell Anemia Control Act; as a result, 10 states, containing more than 40% of the black population of the USA, have introduced laws requiring mandatory, rather than voluntary, screening for sickle-cell haemoglobin (Rutkow and Lipton, 1974). Both of these aspects are now relevant to the care of immigrant patients in the United Kingdom and to the establishment in this country of cooperative clinical trials and community screening programmes. Management of the Sickle-cell Crisis TYPES OF CRISIS The term 'crisis' in sickle-cell disease may be used to describe the vasoocclusive episodes of tissue infarction (painful crisis) or episodes of sudden anaemia resulting from marrow hypoplasia, an exacerbation of haemolysis, or splenic sequestration (haematological crisis). In a paediatric population receiving folic acid supplements we have found that hyperhaemolytic crises and episodes of erythroid hypoplasia are relatively common causes of a profound fall in haemoglobin. These haemolytic episodes may be precipitated by a viral infection associated with cold antibody formation (Cotter, Walker, Bird, Mann, and Stuart, 1974). There is, however, insufficient information concerning the frequency and cause of these hypoplastic, haemolytic, and sequestration crises, and cooperative studies involving investigation and treatment are required. This is particularly important in obstet-26 rical practice because of the high maternal and perinatal mortality (Fort, Morrison, Berreras, Diggs, and Fish, 1971).