Aim: This in vitro study is an attempt to compare the effectiveness in cleaning oval shaped root canals usingAnatomic Endodontic Technology (AET ® ), ProFile system ® and Manual Instrumentation with K-files. Methodology:Sixty oval shaped single rooted maxillary and mandibular premolars with straight canals were divided in to three groups. The root canals were, confirmed as being oval shape by means of radiographs made in a buccolingual and mesiodistal direction. Automated canal preparation was performed using Anatomic Endodontic Technology (group 1) and the ProFile system ® (group 2). Manual instrumentation (group 3) was performed with k-files. Irrigation was performed using alternatively 3% NaOCl and 17% EDTA, followed by rinsing with normal saline. The roots were split longitudinally into two halves and examined under a scanning electron microscope. The presence of debris and smear layer was recorded at distances 1, 5 and 10 mm from the working length using a three step scoring scale. Mean scores for debris and smear layer was calculated and statistically analyzed for between and within groups significance, using the Kruskal-Wallis nonparametric ANOVA test and Bonferroni's multiple comparison test.Results: At 1, 5 and 10 mm levels the root canals prepared with AET had significantly less surface debris and smear layer on the canal walls as compared to canals prepared with ProFile system ® or manual instrumentation. For all three groups significantly lower mean smear layer scores (p < 0.05) were recorded at 5 and 10 mm levels compared with the 1 mm level. Significantly lower mean debris scores (p < 0.05) were also recorded at 5 and 10 mm levels for the AET group whereas no significant differences were found between the three levels for the ProFile system ® and manual instrumentation groups. Conclusion:Although better instrumentation scores were obtained in canals prepared with AET, complete cleanliness was not achieved with any of the techniques and instruments investigated.