Numerous nickel titanium rotary file systems have been introduced in recent years. The recommended speed at which these files are to be operated varies widely between manufacturers. The purpose of this study was to test the number of rotations to fracture of NiTi rotary files when operated at different speeds and at different angles. Sixty size 25 Profile® nickel titanium rotary files were tested, thirty 0.04 and thirty 0.06 taper. Files were operated at speeds of 350 or 600 rpm and at angles of 25°, 28°, and 33.5°. The time to fracture was recorded and the numbers of rotations to fracture were calculated. The data was analyzed using a two-way ANOVA, and post hoc Tukey-Kramer multiple-comparison test with alpha = .001. The results show a significant difference in the number of rotations fracture according to taper and angle. Files of .06 taper fractured more readily than files of .04 taper as the speed increased, and the time to fracture decreased for both tapers as the angle increased. No significant difference was produced by the speed at which the files were operated. The number of rotations until fracture of NiTi rotary files is not related to the operational speed.