Hexane-dioic acid (or adipic acid), C(6)H(10)O(4), crystallizes with two crystallographically independent half-mol-ecules in the asymmetric unit of the triclinic unit cell, space group P, as each mol-ecule lies across a crystallographic inversion centre. A monoclinic polymorph has been reported previously, most recently by Ranganathan, Kulkarni & Rao [J. Phys. Chem. A, (2003), 107, 6073-6081]. The mol-ecules adopt the expected zigzag structure and are linked via centrosymmetric pairs of O-H⋯O hydrogen bonds, forming infinite one-dimensional chains along [011]. These chains are stacked along the a axis. The crystal is further stabilized by weak C-H⋯O inter-actions.