An experimental check has been obtained for the stability theory of stratified viscoelastic media in compression. Model tests have been conducted for both an elastic layer and a viscous layer embedded in a viscous medium and subject to a compression parallel with the layer. The appearance of the folds and the measured wavelengths are in good agreement with the theoretical predictions. For a better interpretation of the tests, the writers present a theoretical evaluation of the time history of deformation for a layer whose folding develops from a given initial departure from perfect flatness. The calculated folding of the layer at various intervals is plotted for different values of the significant parameter.