Single crystals of 4-dimethylaminopyridinium dihydrogen phosphate (DMAPDP) (C7H13N2PO4) were grown by the solvent evaporation method. The three-dimensional structure was solved by the single-crystal X-ray diffraction method which belongs to triclinic crystal system and the molecular arrangements in the crystal were studied. The thermal behaviour was investigated using differential scanning calorimetry (DSC) and no phase transition was identified in the temperature region -150 to 230 degrees C. The thermal parameters-thermal diffusivity (a), thermal effusivity (e), thermal conductivity (K) and heat capacity (C,) of DMAPDP were measured by an improved photopyroelectric technique at room temperature. Dielectric constant and dielectric loss of the grown crystal were evaluated for the frequency range 1-200 KHz in the temperature region 28-135 degrees C. The Vicker's hardness was measured as 42.2 for a load of 98.07 mN. The laser induced surface damage threshold of DMAPDP crystal was found to be 4.8 GW/cm(2) with nanosecond Nd:YAG laser. (c) 2006 Elsevier B.V. All rights reserved.