The purpose of this study was to investigate various properties of citric acid and EDTA solution as decalcifying and cleansing agents in root canal irrigation, and antibacterial effects of citric acid and EDTA solution. Powdered dentin-resin mixtures were used for evaluating the decalcifying effect of citric acid and EDTA solution. Twelve bacterial strains isolated from infected root canals, were used to evaluate the antibacterial effects of citric acid and EDTA solution. Powdered dentin-resin mixture was found to be more soluble in a 0.5, 1, and 2 M citric acid solutions than in a 0.5 M EDTA solution. Citric acid solution showed antibacterial effects on all the bacteria used.