The asymmetric unit of the title compound, C(10)H(10)O(4), which has been isolated from rhizoma Polygonum Cuspidatum, a Chinese folk medicine, contains two crystallographically independent mol-ecules. The mol-ecules are essentially planar, with a maximum deviation of 0.061 (2) Å from the best planes. The crystal packing is stabilized by weak inter-molecular C-H⋯O hydrogen-bonding inter-actions, with a stacking direction of the mol-ecules parallel to [101].