Nanocomposites of conducting polyaniline (PAni) and cadmium sulphide (CdS) has been synthesized via in situ generation of US from highly reactive organometallic cadmium precursor i.e. dimethyl cadmium (DMCd) in N,N'-dimethyl formamide (DMF). UV-Vis absorption spectra of PAni-CdS nanocomposite showed lambda((max)) at about 440-445 nm in addition to the bands present at similar to325 and similar to615 nm due to PAni. The absorption band at similar to440-445 nm is identified due to nanosized US particles indicating a blue shift of about >70 nm with respect to bulk CdS. The X-ray diffraction pattern showed broad peaks due to formation of nanoparticles of US in polyaniline matrix. Scanning electron microscopy (SEM) showed that the particles are in agglomerated form. Organometallic compound i.e. dimethyl cadmium (Me2Cd) is used for the first time with polyaniline for US nano particles. (C) 2004 Elsevier B.V. All rights reserved.