Irrigation is a key part of successful root canal treatment. It has several important functions, which may vary according to the irrigant used: it reduces friction between the instrument and dentine, improves the cutting effectiveness of the files, dissolves tissue, washing effect and an antimicrobial/antibiofilm effect.Sodium hypochlorite is the main irrigating solution used to dissolve organic matter and kill microbes effectively .Ethylenediaminetetraacetic acid (EDTA) is needed as a final rinse to remove the smear layer.The apical root canal imposes a special challenge to irrigation as the balance between safety and effectiveness is particularly important in this area. Different means of delivery are used for root canal irrigation, from traditional syringe-needle delivery to various machine-driven systems. This book present an overview on various irrigating solutions and some new devices to improve the delivery to the apical portion of the root canal system.