Objective To clarify the relationship between clinical manifestation and pathological features of IgA nephropathy (IgAN) patients with mild proteinuria and/or hematuria.Methods Clinicopathological data from 316 biopsy-proven IgAN cases (proteinuria＜1 g/24 h and/or hematuria, and Scr＜133 μmol/L) from our hospital between January 1993 and October 2009 were studied retrospectively. The renal histopathology was quantified according to Lee's grading and Katafuchi's semi-quantitative standard, and the risk factors for renal pathological lesions were evaluated using multifactor logistic regression analysis. Results Among these 316 patients, 123 were male and 193 patients were female. The mean age at the time of renal biopsy was (33.10±10.69) years old. Clinical features were found as follows: hematuria with proteinuria was found in 267 patients (84.5%), isolated hematuria in 24 patients (7.6%), and isolated proteinuria in 25 patients (7.9%). 16.5% of patients had hypertension. The percentages of CKD stage Ⅰ, Ⅱ, Ⅲ were 76.9%, 20.9% and 2.2%, respectively. 31.3% of patients presented Lee's grade Ⅲ or more severe.52.8% of patients had various degrees of glomerulosclerosis. Crescent formation was observed in 20.3% of patients. 22.5% of patients showed tubular atrophy;16.8% showed interstitial fibrosis and 24.7% also had renal vascular lesions. The extent of glomerulosclerosis was negatively correlated with eGFR levels, but positively correlated with the amount of proteinuria and mean arterial pressure (MAP) level (P＜0.05). The score of tubulointerstitial lesion was positively correlated with the amount of proteinuria and negatively correlated with eGFR and hemoglobin (Hb)level (P＜0.05). The degree of renal vascular lesion was also correlated to MAP level positively and eGFR level negatively (P＜0.05). Multifactor logistic regression analysis revealed that proteinuria, Scr and Hb at the time of renal biopsy were independent risk factors for severe renal pathological lesions (Lee's grade Ⅲ or more severe) with odds ratio of 8.564, 1.031 and 0.975 respectively (all P＜0.01). Conclusions Severe renal histological lesions and decrease of renal function may be seen in some IgAN patients with mild proteinuria and/or hematuria. The levels of proteinuria,Scr and Hb are the independent risk factors for severe renal pathological lesions. Renal biopsy is important in these patients in order to make diagnosis and individual treatment.