The enthalpies of sublimation of the six isomers of dihydroxybenzoic acid were determined by thermogravimetry as part of a study to investigate their performance as model matrices in matrix assisted laser desorption/ionisation-mass spectrometry. The enthalpy of sublimation could be determined to within an error of +/-7%. In the MALDI mechanism, sublimation is thought to play an important part, however in the present study no positive correlation between this parameter and the performance of the material as a matrix was found.