Single crystals belonging to LAP family are identified as the most promising semi organic non-linear materials. In the present work, single crystals Of L-arginine di phosphate (LADP) and metal- (Cu and Mg) substituted LADP are grown by slow evaporation method. The grown crystals are characterized by single crystal XRD, FTIR, optical absorption and NLO test. The photoconductivity studies indicate that both pure and metal-doped LADP crystals exhibit positive photoconductivity. (c) 2005 Elsevier B.V. All rights reserved.