Good optical quality single crystals of L-arginine diphosphate C6H20N4O10P2 (abbreviated as LADP) having dimensions up to 30 x 6 x 4 mm(3) are reported. The crystals have been grown by slow solvent evaporation at a constant temperature of 30degreesC from its aqueous solution. The grown single crystals were characterised by employing UV-VIS spectrum, FTIR, DTA, TGA and X-ray diffraction methods. (C) 2002 Elsevier Science B.V. All rights reserved.