Aim: The objective of the present study was to compare the radiopacity of endodontic sealers based on three different chemical compositions: epoxy resin and calcium hydroxide (Acroseal and Sealer 26), zinc oxide eugenol (Endofill, Endométhasone N, N-Rickert), and methacrylate resin (RealSeal). Materials and methods: Three specimens measuring 10 mm in diameter and 2 mm in thickness were prepared from each test material and radiographed next to a 1- to 8-mm-thick aluminium stepwedge using occlusal films. The radiographs were digitised, and optical density was used to determine the radiopacity of the materials according to a greyscale with levels ranging from 0 to 255. The data was submitted to the variance test (ANOVA, P 0.05) as well as to the Ryan-Einot-Gabriel-Welch and Quiot test (REGWQ) for multiple comparisons of the means. Results: The greyscale level means for the materials, in increasing order, were: Acroseal - 125.3; Sealer 26 - 144.3; Endométhasone N - 155; Endofill - 175.3; RealSeal - 183; N-Rickert - 188.3. None of the materials presented a radiopacity mean level significantly lower than that obtained with 4 mm of aluminium (111.3), which was used as a reference to compare the sealers following ANSI/ ADA specification 57 (2 mm thicker than the test specimen). Conclusions: All of the endodontic sealers evaluated presented a radiopacity level above the minimum required. Keywords: dental materials, dental radiography, endodontics, root canal obturation, sealer