Abstract Background and Aims Renal histology in ANCA-associated vasculitides-glomerulonephritis (AAV/GN) is characterized by active (inflammation, necrosis, crescents) and chronic lesions (sclerosis, fibrosis), and lately classified by Berden Classification (BC), ANCA renal risk (RRS) and Mayo Chronicity score (MCCS). We aimed to prospectively compare predictive ability of the three classification models in AVV. Method 27 AVV/GN patients, 17 females, were estimated at time of diagnosis (T0), based on renal biopsy, commenced on the same treatment protocol, cyclophosphamide+steroids, and followed for 6 months. BC, RRS and MCCS Classification models were initially applied on renal biopsies and results were correlated to renal function at T0, and accordingly, 3 (T3) and 6 (T6) months. Results Patients’ median age at presentation was 61.9(18-82) years, ratio of MPO/PR3/ANCA- was 17/7/3, eGFR was 19(19)mg/ml/1.73m2, and 11/27(40.7%) patients were hemodialysis-dependent (HD) at T0. Based to BC model, 5(18,5%), 9(33,3%), 8(29,7%), 5(18,5%) were classified as Focal, Crescentic, Mixed, Sclerotic, respectively, while according to RRS 7(26%), 10(37%), 10(37%) as Low, Medium, High, respectively and to MCCS 3(11%), 13(48%), 6(22%), 5(19%) as Minimal, Mild, Moderate, Severe, respectively. During follow up eGFR significantly increased from T0 towards T3 and T6, 19(19), 34(21), 38.5(26)mg/ml/1.73m2, respectively, p<0.0001. In RRS model, significant improvement was noticed in patients classified as low, eGFR from 37.5(55) vs. 57.5(39) vs. 57(22)mg/ml/1.73m2, p = 0.019) or medium risk group, 31(24) vs. 39(18) vs. 40(10)mg/ml/1.73m2, p = 0.047), at T0, T3, T6, respectively. In BC, a significant increase of eGFR was evident in sclerotic class, 18(9) vs. 32(17) vs. 38(21)mg/ml/1.73m2, respectively p = 0.05. RRS showed important results regarding HD dependence. At T0, from the 11 HD patients 1/3/7 were classified as low/medium/high risk, p = 0.04, the ratio changed to 0/1/5, respectively, p = 0.02 at T3 and 0/1/4, p = 0.04 at T6. No patient with low risk RRS remained on HD, while, 7/10 patients with high RRS, were still on HD at T6. BC and MCCS could not predict end stage renal function either at 3 or 6 months of follow up. Conclusion In the short term follow up, ANCA renal risk could better predict renal function outcome compared to Berden Classification and Mayo Chronicity Score, with high RRS frequently leading to HD. Instead, the sclerotic class in BC was not predictive of poor outcome.