Aim: To compare the amount of apically debris extruded following root canal preparation with One Shape, Two Shape and Revo-S NiTi rotary file systems.Materials and Methods: Forty five extracted mandibular human first molars were selected nearly 20 to 22 mm of length average. The access cavities were prepared and the MB canals were localized and explored with a size 10 K-type file. The distal roots of all teeth were amputated to the cervical level and their orifices were sealed with glass ionomer filling material. The teeth were radiographed with a file in MB canal, and the canals with a curvature degree 10 to 20 were included in this study. Apically extruded debris was collected in pre-weighted collector tubes by 10-4 precision microbalance. The teeth with the collector tubes were randomly assigned to three groups, fifteen for each. Group I, MB canals were prepared by using One Shape, Group II, MB canals were prepared by using Two Shape and Group III, MB canals were prepared by using Revo-S NiTi rotary files to the tip sizes 25 and taper of 0.06. Irrigation was performed with bi-distilled water in exactly the same manner for all the specimens with 27-G irrigation needle. All tubes were put in a receptor and were taken to an incubator where they were stored at 37oC for 21 days until the debris was dry. The tubes were then reweighted using the same analytical balance. The difference between pre-weighted tubes and the weight after preparation were tabulated and compared statistically. Results: The lowest amount of apically extruded debris was found in Two Shape group followed by One Shape group, and the highest amount was found in Revo-S group. Comparison between the mean values of the three groups revealed a statistical significant difference at 5%.Comparison between the Two Shape group and One Shape group revealed a statistical significant difference at 5%. Comparison between the Two Shape group and Revo-S group revealed also a statistical a significant difference at 5%. But no statistical significant difference revealed when comparing the One Shape and Revo-S groups at 5% level of significance.Conclusion: The Two Shape showed significantly the lowest amount of apical debris extrusion followed by One Shape and the highest amount showed by Revo-S.