Single crystals Of L-histidine hydrofluoride dihydrate (LHHF), a semiorganic nonlinear optical (NLO) material have been successfully grown by slow evaporation technique. The crystals were characterized by X-ray diffractometry (XRD), Fourier transform infrared (FTIR), UV-Vis-NIR, TGA, DTA, microhardness and solubility studies. The SHG efficiency of LHHF was found to be higher than that of KDP. The dielectric constant and dielectric loss of the crystal was studied as a function of frequency and the results are discussed. Photoconductivity studies carried out on the sample revealed its positive photoconductivity nature. (c) 2006 Elsevier B.V. All rights reserved.