A mandibular first molar with more than four canals is an interesting example of anatomic variations, especially when four of these canals are located in distal roots. This report describes a case of a mandibular first molar with six canals (two mesial and four distal canals in two distal roots). The canals were equipped with a K-file and irrigated with NaOCl (5.25%) and normal saline as the final irrigant. The canals were filled laterally with gutta percha and AH26 sealer (De Trey, Dentsply, Switzerland). This case shows a rare anatomic configuration and points out the importance of looking for additional canals.