Reliability of death certificate diagnoses. Consistency between death certificates and clinical records from 5 general hospitals in Kuwait was studied for 470 deaths with the following underlying or associated causes: hypertensive (HYP), ischaemic heart diseases (IHD), cerebrovascular diseases (CVD) and diabetes mellitus (DM). Direct causes were not considered since they are of little interest analytically. Only deaths with definite or most probable ascertainment were included. One cardiologist, who was provided with the WHO criteria and relevant documents on death certification, independently reviewed the records. To test the reviewer's bias and the reliability of his judgement, an adjudication process was effected by having one senior cardiologist re-review a random subsample of 140 records. The two reviewers showed good agreement. Specific diagnoses criteria for deciding the underlying cause of death in multiple morbid conditions by the reviewer were followed. Due to possible reviewer bias, we aimed at measuring the difference between initial certifiers and the reviewer rather than measuring the diagnostic accuracy of initial certifiers in reference to the reviewer. The agreement index kappa showed poor agreement between original and revised certificates. The original certificates under-estimated CVD as an underlying cause of death by 69.2%, DM by 60%, IHD by 33.5% and HYP by 31.8% in our sample. Associated causes were also consistently under-estimated by initial certifiers as compared with the reviewer. This bias calls for basing mortality statistics in Kuwait on hospital death committees' reports rather than on initial certifier death certificates, use of multiple-causes of death instead of one underlying cause and adequate training of the medical profession on the value and process of death certification. 