Introduction: This study evaluated the cross section, resistance to bending and buckling of Reciproc and WaveOne instruments. Methods: Reciproc R25 (VDW, Munich, Germany) and WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) instruments, all of them 25-mm long, with D0 diameter of 0.25 mm and taper of 0.08 mm/mm along the first 3 mm from the tip, had their cross section analysed and were subjected to bending and buckling resistance tests. The data from both tests were analysed using the Student t test. Results: A statistically significant difference was observed between the maximum load to bend Reciproc 25 and WaveOne Primary instruments (P 0.05). Higher values were necessary to bend WaveOne Primary instruments when compared with Reciproc R25. In contrast, there was no statistically significant difference between the maximum load to buckle Reciproc 25 and WaveOne Primary instruments (P > 0.05). Conclusions: Both instruments exhibited similar behaviour in terms of buckling resistance. However, Reciproc R25 was more flexible, which is an important instrument property for the shaping of narrow and curved root canals. Keywords: bending resistance, buckling, M-Wire, nickel-titanium, reciprocating technique