It is of crucial importance to evaluate disease activity by means of endoscopy and histopathology in Crohn's disease (CD). Nonetheless, correlation between endoscopic and histological validated indices has not been verified. We aim to correlate the Simple Endoscopic Score for Crohns disease (SES-CD) with two validated widely used histological indices in patients with established CD. The SES-CD at the worst affected area was scored and histological disease activity using Global Histologic Disease Activity Score (GHAS or D'Haens score) and the Naini and Cortina Score (NCS) was scored independently by two pathologists blinded to the clinical information and endoscopic results. Spearman correlation between the SES-CD, GHAS and NCS were performed. 143 patients, 32 with SES-CD scores 0-2, 57 with 3-6, 37 with 7-15, and 17 with ≥16. Correlation coefficients between SES-CD and GHAS were r = 0.86 (95% CI 0.80-0.91, p < 0.001) and between SES-CD and NCS r = 0.85 (95% CI 0.81-0.88, p < 0.001). There was a strong correlation between the two histological indices (r = 0.70, 95% CI 0.59-0.78, p < 0.001). Mucosal healing without histological disease activity was most correlated with SES-CD score 0 or 1. The SES-CD strongly correlates with both GHAS and NCS. The SES-CD of 0 to 1 best represents histological remission that correlates with quiescent disease activity. Copyright © 2019 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.