Aim To investigate the relationship between angiotensin converting enzyme (ACE) gene polymorphism and microalbuminuria in patients with essential hypertension Methods Polymerase chain reaction (PCR) was used to determine the genotypes for an insertion/deldtion polymorphism of the ACE gene in 50 hypertensive patients with microalbuminuria and 49 hypertensive patients without microalbuminuria and 50 healthy controls. Urine MAlb concentrations were determined by radioimmunoassay. Results There was significant difference in the frequencies of D allele and DD genotype between hypertensive patients with microalbuminuria and healthy controls. The frequencies of D allele and DD genotype was higher in hypertensive patients with microalbuminuria and lower in those without microalbuminuria. However, ACE I/D polymorphism did not differ in hypertensive patients with non microalbuminuria and healthy controls. Conclusion ACE gene polymorphism was closely related with hypertensive microalbuminuria. DD genotype was possibly involved in the renal injury in patients with hypertension.