The accomplishment of endodontic treatment depends on diagnosis of all the canals, thorough biomechanical preparation followed by three dimensional obturation with hermetic seal. Missing any of these steps may occur dueto bizarre tooth morphology. Usually mandibular molars have two roots with three canals (mesiobucccal, mesiolingual & distal) but in some teeth, the number of roots and canals vary. The variation in the number of roots is called radixentomolaris. This article presents three case reports of mandibular first molars with extra roots. Also mentioned are the modifications in the canal preparation, problems encountered during the treatment, common iatrogenic errors which occur during the treatment and factors which affect the prognosis.