For this reason, few data on cause-specific mortality are available for developing countries iv the main international sources, the WHO Statistics Annual and the UN Demographic Yearbook. In the WHO Statistics Annual, which shows cause-specific death rates by age-group and sex, data are available for several of the Latin American countries, where vital registration systems are relatively well developed. In Africa, however, only Mauritius now reports regularly, although data are available from Egypt for 1975. Among the developing countries of Asia, data are available only for Thailand and Sri Lanka, but the data for Sri Lanka appear to be incomplete, no deaths being reported from respiratory, gastro-intestinal, neurological, endocrine, nutritional or genito-urinary causes. More countries are represented in the UN Demographic Yearbook, but data here are for all ages combinled, so that the large number of childhood deaths cannot be separated from those of adulthood and old age.

The low coverage of vital registration in many of the developing countries results from several factors, including a lack of incentives to register deaths, and the lack of locally sited offices at which deaths may be registered. A shortage of doctors, especially in rural areas, is often an additional factor in countries where the death certificate has to be completed by a medically qualified person. Where deaths are registered, the usefulness and reliability of the ce~rtified cause-of-death are often questionable, partly because many peopTe die at home, often without being given any kind of medical care, and partly because the certification of cause of death is often performed by someone without medical qualifications. This is reflected in the large proportions of deaths classified in ill-defined categories. Even where certification is performed by a physician, its accuracy may not be high. The accuracy of cause of death as shown on death certificates has been shown to be low even in some developed countries, where staff and facilities are plentiful (Alderson and Meade, 1967). Post-mortem studies often show disagreement between clinicians and pathologists. For example, a study in Connecticut, USA, showed a major disagreement on the underlying cause in 29% of deaths (Kircher et al. 1985). Also, inaccurate completion of certificates may result in incorrect classification of the underlying cause of death. Fuller (1985) found in a study in the UK of deaths of known diabetics, that diabetes was mentioned on the death certificate in only 54% of cases. Such under-reporting of underlying causes is likely to be even more serious in developing countries.

Deficiencies in the coverage and reliability of vital registration may lead to considerable distortions in the reported distribution of causes of death. It is probable that deaths from some causes are more likely to be registered than those from other causes. For example, registration of deaths is usually more complete in urban centres, leading to a bias towards those causes of death that are especially common in such areas, but even within a given area there may be a tendency for deaths from some causes to be registered more often. Distortion will also be caused by variations in the reliability of diagnosis of different causes. Thus, deaths from cancer are likely to be under-diagnosed in developing countries because of a lack of facilities and trained staff. On the other hand, reporting of conditions such as tuberculosis (TB), for which relatively well 4