Success of endodontic treatment depends on the proper scouting identification and thorough chemo mechanical preparation of all the canals followed by three dimensional obturation .The prime Failure to achieve this steps may be due to unusual tooth morphology. Usually mandibular molars have two roots with three canals (mesiobucccal, mesiolingual & distal) but in few teeth, the number of roots and canals vary. The variation in the number of roots is called radix entomolaris.(1) This article presents five 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.