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).