The mortality due to ischemic heart disease may be assessed in the department of the Haute Garonne from a Register of cardiovascular disease. In this study the medical causes of death codified using the normal criteria of international classification of disease were compared with the causes of death classified according to the criteria of the Register determined in the same subjects after a complementary enquiry. Between July 1st 1984 and December 31st 1986, 800 consecutive cases of patients dying of cardiovascular disease aged 25 to 64 years at death were examined. A complementary enquiry into the cases of these patients was undertaken involving the treating physician and hospital establishments in order to determine the mode of death and to obtain clinical, ECG, biological and when possible autopsy results for each case. The sensitivity and specificity of the causes of death coded 410-414 according to the criteria of international classification of disease was 74 and 71 p. 100 respectively. The positive predictive value was 75 p. 100 and the value of the kappa index was 0.44. Therefore, the concordance between the causes of death codified by the usual classification and those codified after a thorough complementary enquiry was not very close. On the other hand, taken as a whole, the number of deaths due to ischemic heart disease by the international coding system (428 cases) was 2.1 p. 100 less than that observed after the complementary enquiry (437 cases). These results should, however, be interpreted with caution because of the high proportion (34%) of cases in which the cause of death could not be determined with precision even after the complementary enquiry.(ABSTRACT TRUNCATED AT 250 WORDS)