Background In the late 1980s and early 1990s a generalized HIV epidemic affected Thailand which was relatively well controlled by an intensive national campaign by the mid 1990s. The extent to which the epidemic has slowed or possibly reversed the epidemiological transition in Thailand is relatively unknown.

Methods Under-five mortality rates (U5MR) were determined from various sources and weighted least squares regression conducted to determine U5MR over the years 1980–2000. Direct and indirect estimates of the completeness of death registration were used to estimate mortality levels in those aged more than 5 years for the 1980–90 and 1990–2000 periods. Life tables were constructed using the various estimates to determine changes in life-expectancy between the two time periods.

Results U5MR in Thailand is estimated to have been 58/1000 live births in 1980, declining to 30 in 1990 and to 23 in 2000. The vital registration system clearly underestimates U5MR. Successive surveys of Population Change (SPC) imply coverage of death registration improving from 75–77% in 1985–86 to 95% in 1995–96, partly due to a reliance on self-reported registration in the latter survey. In contrast, the General Growth Balance–Synthetic Extinction Generations (GGB–SEG) method suggests coverage worsening from 78–85% in 1980–90 to 64–72% in 1990–2000. Life tables based on SPC adjustments show continued declines in female, and to a lesser extent, male adult mortality with corresponding increases in life-expectancy at birth of around 6 years for both sexes from 1980–90 to 1990–2000. In contrast, the indirect adjustments suggest a substantial increase in male adult mortality with female adult mortality unchanged; life expectancy decreased by 4 years for males and was only marginally higher in females.

Conclusion Given the conflicting evidence a definitive assessment of mortality change in Thailand between 1980 and 2000 is difficult to make. Indirect adjustments, based on demographic methods point to a major reversal in mortality decline among males, and a slowing in females. If adult mortality registration has declined, and given the continued under-registration of infant and child deaths, remedial measures are urgently required if the mortality system is to better inform and monitor health development in Thailand.