The purpose of this study was to compare the number of rotations to failure of three different rotary file systems. ProFile, Sequence, and Liberator files in sizes 25 and 40 with 0.04 taper were divided into groups of five and rotated against a grooved metal block mounted to a Universal testing machine at 31 and 34 degrees. Each file was rotated at 300 rpm until fracture occurred. The number of rotations to fracture were calculated. Use of a three-way ANOVA and Tukey's HSD multiple comparison tests revealed significant differences for the angle of deflection, size, and type of file. An increased angle of deflection resulted in a decreased number of rotations to failure for all three file types. An increased size of file also resulted in a decreased number of rotations to failure in all the groups. Liberator and Sequence files required fewer rotations to failure than ProFiles in all groups tested except the size 25 files rotated at the less severe angle. ProFiles appear to be more resistant to flexural fracture than Liberator and Sequence files unless the files are of smaller size with a less severe curvature. Care should be taken to limit the number of uses when using larger size files, especially Liberator and Sequence files, around severe curvatures.