Crystal structures have been determined for both (+)-and (±)-7,7-dimethyl-2-oxobicyclo[2.2. 1 ]heptane- 1 -carboxylic acid, C 10 H 14 O 3 . The asymmetric unit of the (+)-form, (I), contains two molecules paired by mutual hydrogen bonding of their carboxyl groups, without ketone involvement. Both carboxyl groups are disordered and the conformation of each relative to its own molecule differs by 46.3 (4)° for the two halves of the dimer. In the racemate, (II), the asymmetric unit also contains two molecules, each of which dimerizes with a centrosymmetric counterpart by mutual hydrogen bonding of carboxyl groups across the a or b cell edge, also without ketone involvement. Besides disorder of the carboxyl C-O lengths and angles, each half of the asymmetric unit of (II) displays extensive enantiomeric disorder, corresponding to transposition of the ethylene and methylene bridges, with the carboxyl and ketone C atoms plus the anti-methyl C atom exactly coinciding. Each contributor to the structure of (II) has a different rotational conformation for its carboxyl group, none corresponding to those found in (I).