Objective To characterize the intrarenal arteriole lesions and the possible pathogenesis in IgA nephropathy patients with and without hypertension. Methods We retrospectively collected 20 IgA nephropathy patients with mild mesangial hyperplasia or focal hyperplasia associated with intrarenal arteriole lesions. They were divided into two groups: group A with normal blood pressure (n=10), and group B with hypertension (n=10). In addition, 10 non-IgA nephropathy cases with mild mesangial hyperplasia or focal hyperplasa and normal blood pressure were assigned as group C. Clinical and pathological indexes were matched among the 3 groups. Renal biopsy tissues were subject to light microscopy after HE, PASM and Masson staining, immunofluorescence and electron microscopy examinations. Cross section images of arterioles in the slides were taken after staining with PASM. The wall thickness/outer diameter ratio and intima thickness/outer diameter ratio of the arterioles were then measured. AngiotensinⅡ (Ang II), AngiotensinⅡ receptor type I (AT1R) and collagen III in slides were detected by immunohistochemistry. Results The wall thickness/outer diameter ratio and intima thickness/outer diameter ratio of the arterioles were significantly higher in groups A and B than in group C, but were indifferent between group A and B. The expression of AngⅡ and AT1R in renal tissues and arterioles were significantly higher in groups A and B than in group C. AngⅡ expression in renal tissues was significantly higher in group B than in group A, but AngⅡ expression in arterioles and AT1R expression in renal tissues and arterioles were similar between the 2 groups. Collagen III expressed predominantly in arteriolar intima, and was significantly higher in group B than in groups A and C. Positive correlations between wall thickness/outer diameter ratio and AngⅡ expression as well as between intima thickness/outer diameter ratio and the expressions of AngⅡ and AT1R were found in arterioles. Conclusion In IgA nephropathy patients, the intrarenal arteriole lesions did not correlate to hypertention, and the intrarenal rennin-angiotensin system is highly expressed.