Semiorganic nonlinear optical material 2-amino-5-nitropyridinium bromide (2A5NPBr, molecular formula C5H6O2N3Br) has been synthesized, and single crystals of size 10 x. 7, 3mm(3) have been grown from its aqueous solution of pH = 2.04 at room temperature by solvent evaporation technique. The grown crystals have been characterized by X-ray diffraction to determine the cell parameters. and b FT-IR and NMR techniques to confirm the formation of the expected compound. The thermal stability of the compound has been determined by TG DTA curves. The UV-vis-NIR transmittance and the powder SHG studies have also been carried out. (c) 2005 Elsevier B.V. All rights reserved.