Statement of problem: Perforation is one of the most important problems which may occur during root canal therapy. To repair the perforation and to cut the relation of the root with the tissue of its peripheral environment, materials with adequate sealing ability and suitable price are needed.Purpose: The aim of this study was to survey the microleakage of the three materials in the restoration of lateral perforations in the roots of the teeth.Materials and method: In this experimental study, 54 intact molar teeth were selected and assigned randomly to three groups. Canals were prepared with stepback technique and perforations were made at the apical third of the roots. The cavities were restored with MTA, Root MTA and Portland Cements type І. The positive control group was subjected to perforation but no perforations were made in the negative control group.  The teeth were covered with two layers of nail varnish restoring in 2% fushin solution for 24 hours after incubation. The teeth were sectioned and their leakage was measured by stereomicroscope. The records were analyzed by one- way ANOVA and LSD (Least Square Differences) test.Results: In the positive group dye was completely entered in all perforation areas while no leakage was observed in the negative group. The statistical test showed no significant difference between MTA and Root MTA groups in terms of leakage (p>0.05). But MTA and Root MTA had significant differences with Portland cement (p<0.0001).Conclusion: Considering the results of this study, Root MTA may be considered as a substitute for Pro Root MTA in root canal treatment; however, usingPortland type I cement needs more investigations.  Key words: Microleakage, Perforation, Pro Root MTA, Root MTA, Portland cement