The OH radical can attack the CH3SH molecule by hydrogen abstraction reactions from the methyl group, R1, and from the sulphur atom, R2, the latter being the dominant path in the temperature range 200-2000 K. In the present paper an analytical fulldimensional potential energy surface, named PES-2024, was developed for the first time for this eight-body system with 18 degrees of freedom. Within the valence bondmolecular mechanics framework, the new surface was fitted to high-level ab initio calculations using a reduced number of points, the input data. In order to check its quality, it was subjected to a series of stringent tests. Firstly, for both the R1 and the R2 paths, PES-2024 reasonably reproduces the ab initio input data used in the fitting process, such as high exothermicities, low barriers and stability of the intermediate complexes in the entrance and exit channels. As these data were used in the fitting process, obviously this represents only a self-consistency test. A second test was carried out considering zones not included in the fitting. Now the error is slightly larger, but as they appear in repulsive zones (associated with very high energies) we suppose that will have little influence on the dynamics of the reaction. A final test of quality has been to show its capability to reproduce experimental dynamics properties.