Investigation of the hydrolysis of dinucleoside-arsenate-deoxyguanylyl-3′,5′-deoxyguanosine (dGAsdG − ) reveals that base-stacking in DNA increases the resistance of As–DNA towards hydrolysis . Base-stacking raises the activation energy of hydrolysis . Hydrolysis of As–DNA is found to be endothermic. The hydrolysis stability of As–DNA should be higher than that estimated based on arsenate diester models.