Transmission electron microscopy using the dark field mode of imaging has been demonstrated as a useful method for the structural characterization of Langmuir-Blodgett (LB) thin films and for revealing the presence of holes in such films. In this paper, we show that the presence of such holes may be related to the nature of the substrate used to support the LB films and that some substrates, notably amorphous carbon, may be unsuitable for this purpose. In addition, real-time electron microscopy studies reveal that holes may, in some materials at least, be created by the action of the electron beam. © 1990.