All national vital registration data mask variations in cause-specific mortality between different areas within a country. In Brazil in 1984, for example, intestinal infectious diseases were the leading cause of death (for all ages combined) in the state capitals of the Northeast, but did not appear in the leading ten causes in the state capitals of the South or Mid-West (PAHO, 1988).

Turning to registration data for sub-national populations (Table 4), there are difficulties of comparability because different reports use different disease groupings. In their report of data for the black population of rural South Africa, Botha & Bradshaw (1985) only give the percentages of deaths accounted for by six of the main headings of the ICD. External causes accounted for 30% and circulatory diseases for 18% of all adult deaths. External causes and circulatory diseases were alsc the two leading causes of death in Lagos, Nigeria (Ayeni, 1980). Motovehicle accidents alone accounted for 26% of deaths of persons aged 15t, while circulatory diseases accounted for 20%. Fargues and Nassour's (1987) analysis of deaths registered in Bamako, Mali gives death rates by five-year age-groups for 13 cause categories. Table 4 shows a crude average of the dea'- rates for the age-groups from 15 to 64 years, indicating the mos. important causes of adult death to be liver disease, cardiac insufficiency, TB and !ntestinal infectious diseases.

Table 5 summarises the leading causes of death from sources other than vital registration. Comparison of the results of these studies is subject to serious difficulties because of widely differing methods of classification and tabulation. This is exemplified by the hospital data from West Nile District, Uganda (Williams et al, 1986). Data are given only for those individual causes of death associated with 30 or more deaths, and this accounts for only 312 of the 679 adult deaths. The leading causes of death recorded in this hospital study were schistosomiasis, pneumonia and gastrointestinal diseases, together accounting for about 25% of the deaths. It is surprising that no deaths from circulatory disease or external causes appeared among the leading causes in this study. These data, however, should be interpreted with great caution in view of the substantial presentation biases inherent in a study of deaths at a hospital covering a large rural catchment area. In the other hospital-based study in Madras, India, TB, suicide and cardiovascular disease were the leading causes of death. If deaths from suicides and accidents are added, external causes were clearly the leading cause of death in this study. It is of interest that of deaths from external causes, over half the male deaths and nearly all the female deaths were attributed to "suicide and self-inflicted injury".

The longitudinal study of factor., workers in Senegal (Borges da Silva, 1987) showed liver disease to be the leading cause of death, as in the report from the neighbouring country of Mali described above, accounting for 41 (25%) of the 164 deaths. Carcinoma of the liver accounted for 22 of these deaths, hepatitis for 10 and cirrhosis for 9. In Table 5, these deaths have been reclassified such that, as in most official statistics, carcinoma of the liver is included under neoplasms and hepatitis with infectious diseases. Borges da Silva gave separate figures for accidents at work (13% of deaths) and other accidents (10%). When these are combined, accidents again become the leading cause of 9