Growth of good optical quality single crystals of L-arginine diiodate (abbreviated as LADI), a serniorganic nonlinear optical (NLO) material is reported. Crystals of dimension up to 14 x 6.5 x 5 mm(3) were obtained from its aqueous solution by slow solvent evaporation technique. The crystals were characterized by single crystal XRD, FTIR, optical absorption spectrum, microhardness, dielectric and photoconductivity studies. The DTA and TGA traces of LADI confirm the decomposition of the sample at 145 degrees C. (c) 2006 Elsevier B.V. All rights reserved.