Films of CuO nanowhiskers with diameters in the range of 50 to 300 nm and lengths of up to several microns were prepared by employing reactions at the liquid-liquid interface. In this method, a precursor of copper acetyl-acetonate taken in the toluene layer reacts at the interface with hydrolyzing agent in the aqueous layer, at a,temperature of about 50 degrees C. The crystallinity, purity, morphology and structural features of the as-prepared film were studied by using X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Results reveal that the film obtained is of densely packed nanowhiskers with large aspect ratios and having a crystallinity of monoclinic CuO. (c) 2005 Elsevier B.V. All rights reserved.