Single crystals of L-lysine acetate, an organic nonlinear optical (NLO) material, were grown by the controlled evaporation of its aqueous solutions. Its solubility in aqueous solution was determined gravimetrically. The grown crystals were characterized by the single-crystal diffraction, X-ray powder diffraction, Fourier transform infrared and Raman spectra. The structure analysis reveals that it belongs to the monoclinic crystallographic system, space group P2(1), with cell parameters: a = 5.420(2)angstrom, b = 7.542(4)angstrom, c = 12.653(1)angstrom, P = 91.73(1)degrees, Z= 2 and V= 516.8 angstrom(3). Experiments of thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to study its thermal properties. The optical behaviours, including transmission spectrum and second harmonic generation (SHG), were investigated to study its linear and NLO properties. (c) 2008 Elsevier B.V. All rights reserved.