Single crystals of bis thiourea cadmium iodide[CdI2(CH4N2S)(2)], abbreviated as BTCI, a semiorganic material has been successfully grown by both slow evaporation and slow cooling methods. Crystal of dimensions up to 3.3 x 1.0 x 1.5 cm(3) is reported. Single crystal X-ray diffraction analysis has been carried out to confirm monoclinic system and etching studies for their perfection. The morphology of the grown crystal was also identified by single crystal X-ray diffraction analysis. The powder X-ray diffractogram of the crystal has been recorded and the various planes of reflection are identified. The presence of functional groups and the coordination of metal ions to thiourea were confirmed by FTIR analysis. Transmission spectra reveals that the crystal has low UV cutoff of 324 nm and has a good transmittance in the entire visible region enabling its use in optical applications. The thermal behaviour of the crystal has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), which indicates that the material does not decompose before melting. Studies of dielectric properties (dielectric constant and dielectric loss) both as function of frequencies (100 Hz to 5 MHz) for varying temperatures in the range 308-348 K suggests good candidate for electro optic modulators. (C) 2008 Elsevier B.V. All rights reserved.