The frequency of twin occurrence in saccharin crystals grown from ethanol and acetone has been quantified and the solubility of saccharin in these solvents measured. Structural and thermodynamic interpretation of the data are consistent with a solvent dependence of both the molecular structure of the (10 (2) over bar) surface (the twin plane) and the identity of the growth synthon. In acetone solutions this surface is terminated by the polar functional groups of saccharin and the crystal grows from a solution rich in monomer species, while in ethanolic solutions it is terminated by aromatic hydrogens and the growth solution is rich in dimeric species. This is the first time that such a combined study of solution and solid-state chemistry has led to a clear indication of how surface structures may change with solvent.