OBJECTIVE To identify the insertion/deletion(I/D) polymorphism of angiotensin-converting enzyme(ACE) gene in Chinese hypertensives complicated with brain infarction. METHODS ACE genotyping with polymerase chain reaction(PCR) was performed in 62 unrelated healthy controls, 55 hypertensives without cardio-cerebrovascular diseases and 44 hypertensives complicated with brain infarction (all controls had no hypertension family history, while the cases had hypertension family history). RESULTS No significant differences could be detected between ACE gene I/D polymorphism and hypertension. However,the frequencies of DD genotype and deletion allele among hypertensives complicated with brain infarction (29.6% vs 56.8%) were higher than those among healthy controls (12.9% vs 38.7%, P<0.05 and P<0.01) and those among hypertensive without cardio-cerebrovascular diseases(12. 8% vs 40%, P<0.05 and P<0.02). CONCLUSIONS A deletion polymorphism of ACE gene is probably an important hereditary factor of brain infarction's morbidity in Chinese hypertensives. The detection of ACE genotypes in hypertensives would improve the early diagnosis of brain infarction.