Mortality statistics are used in epidemiology and public health as an indicator of health status, to evaluate health programs, and in population studies to compare trends and spatial differences. One of the variables used in this type of analysis is the underlying cause-of-death. However, the quality of cause-of-death statistics based on the information recorded by physicians in death certificates has been criticized. The aim of this paper is to discuss the reliability of cause-of-death data recorded by physicians in death certificates, based on studies carried out according to various methodologies, and to comment on the validity of using such underlying cause-of-death statistics.