ABSTRACT The aim of this study was to evaluate the obturation quality in severely curved canals. Thirty-six root canals (angle of curvature > 35o) were used. They were instrumented to 35/.04 BioRaCe, and were divided into 3 groups: lateral compaction, System B/ Obtura, Thermafil. Roots were sectioned at 0mm, 3mm and 5 mm from working length and observed in stereomicroscope (x6). Total area of voids and the maximum penetration of filling materials in isthmuses were measured with image J. For statistical analysis One-Way ANOVA, Kruskal Wallis and Wilcoxon tests were used. There was no statistically significant difference in the total area of voids among groups. Cross-section at 0 mm produced higher total area of voids than cross-section at 5 mm. Penetration of filling materials into isthmuses was deeper in System B/ Obtura. All the examined methods exhibited similar obturation quality, though material with System B/ Obtura penetrated deeper into isthmuses. Keywords: BioRaCe, isthmus, obturation, stereomicroscope, voids.