A review is given of the methods of determining the structure of organic thin films using short-wavelength radiations. These include X-rays, electrons and neutrons. Most of the methods involve diffraction and interference effects, of either traveling or standing waves. In addition, direct imaging techniques are also mentioned. Particular emphasis is given to the structure of Langmuir-Blodgett films but the applicability extends to thin polymer films as well. Some trends of the research in this field are identified. © 1987.