This is a redetermination of the structure of the title compound, C(7)H(6)O(2), which was first reported by Iwasaki [Acta Cryst. (1977 ▶), B33, 1646-1648]. The results are obtained with greater precision in the present study. Crystal packing is stabilized by inter-molecular O-H⋯O inter-actions between the hydroxyl and aldehyde groups which link the mol-ecules into chains in a zigzag pattern along the [110] plane of the unit cell.