The renin-angiotensin system (RAS) is now well established as an important determinant in the progression of renal damage. The level of plasma angiotensin converting enzyme (ACE) is genetically determined and this gene effect is associated with insertion (I)/deletion (D) polymorphism in intron 16 of ACE gene. It has been reported that DD genotype of ACE gene is associated with a poor outcome in patients with IgA nephropathy and trend to develop renal damage in diabetic mellitus. In this study, the correlation between ACE gene I/D polymorphism and the clinical features of lupus nephritis (LN) was determined in 144 LN patients and 150 normal controls by PCR. 72 LN patients were followed up for more than two years. It was found that the DD genotype was significantly higher in LN patients than in normal controls (P < 0.01), while the II genotype was much less in LN (P < 0.01). There was no significant difference in DI genotype frequency between LN patients and normal control (P > 0.05). Patients with hematuria, type IV LN, activation of LN, crescentic formation and severe tubulo-interstitial lesions showed an excess of the DI genotype. However, the DD genotype was not associated with the clinical and pathological characteristics of LN. To assess whether ACE genotype influence the progression of LN, we compared the clinical and pathological findings in patients of different genotype subgroups. There was no significant difference in blood pressure, proteinuria, serum creatinine, active index of disease and crescentic formation at presentation among these groups. However, as patients were divided into two groups according to their rate of decline in renal function. We found that patients with progressive renal function damage had a higher frequency of DI genotype than those with stable renal function (P < 0.01). It is conclude that patients with LN the DI genotype was associated with the severity and the poor prognosis in patients with LN.