Ammonium malate (AM), an organic nonlinear optical material, has been synthesized and single crystals, with dimensions up to 38 x 35 x 27 mm(3), have been grown from aqueous solution. The crystal structure of AM has been determined, and it belongs to the non-centro symmetric space group Cc. The structural perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectroscopic studies were also performed for the identification of different modes present in the compound. The UV-vis transmission spectrum has been recorded in the range 200-1100 nm. The second harmonic conversion efficiency of AM was determined using the Kurtz powder technique; it was observed to be greater than that of KDP. Thermal behaviour of AM was studied by TG and DTA. The dielectric and mechanical behaviour of the specimen was also studied. (c) 2008 Elsevier B.V. All rights reserved.