The experimental observation of electric-field-induced instabilities of polymer films exposed to toluene vapors is reported. When using a laterally structured electrode, the pattern that forms in the polymer film is governed by the interplay of the intrinsic film instability and the periodicity of the electrode structure. By adjusting the applied voltage, it is possible to switch between two different pattern-replication modes. A further important parameter is the aspect ratio of the structured electrode. For high ratios of polymer film thickness to capacitor-plate spacing, structures with hierarchical length scales have been observed.