Aims: This ﬆudy evaluated changes in working length (WL) and root canal dimension after inﬆrumentation with hand inﬆruments (St.St, NiTi) and rotary syﬆems (RaCe, ProTaper). Materials and Methods: Twenty four resin blocks with a curve canal of 33°angle at (14mm) were selected for this ﬆudy. Working length was measured by a digital measurement using a number (10k) ﬁle under ﬆereomicroscope at 40X. The speciﬁc sequence of inﬆrumentation was syﬆem according to manufacturer’s recommendation. The working length of the canal was measured again between each ﬁle and at the end of inﬆrumentation. Pre and poﬆ-inﬆrumentation microscopic photographs were taken and measurements of the root canal dimension change were measured with an image analysis programme . The diﬀerence in working length was analyzed using ANOVA and Duncan’s teﬆ at 5% level of signiﬁcance. Result: Statiﬆical analysis showed that there was no signiﬁcance diﬀerence in the changing of the working lengths and canal dimension between the two rotary syﬆems (ProTaper,RaCe). While there was a signiﬁcant diﬀerence in the changing of the canal length and dimension between the two rotary syﬆems (ProTaper,RaCe) and the hand inﬆruments (St.St, NiTi). The amount of variation in working length and canal dimension obtained with both types of rotary inﬆruments, was signiﬁcantly less than that produced by hand inﬆruments. Conclusion: The variation in working length were clinically not very signiﬁcant between the two rotary NiTi inﬆruments (ProTaper, RaCe)while it was signiﬁcant with the hand inﬆrument (St.St and NiTi).