Holographic structures have been obtained in porous silicon (PS) by photodissolution of the material in hydrofluoric acid under interferometric illumination. This process can be performed after or during the formation of the PS layer. One- or two-dimensional structures have been easily etched down to the submicron range. The photosensitivity is demonstrated for the entire visible range. Because the dissolution process occurs in the bulk, the thickness of the structure is only determined by the penetration depth of the light in the material, which in the case of PS is about 0.1 to 15 μm (from uv to 600 nm). The technique is generalized to all types of nanoporous silicon. The efficiency of the dissolution depends on the specific area of the porous material and the initial resistivity of the wafer. The structures have been characterized by light diffraction. For this material, photoluminescence allows the topography of the porosity modulation to be determined precisely. These results and the ease and low-cost fabrication of the PS layer make porous silicon a promising material for holography.