The possibility to realize three-dimensional (3D) photonic crystals and the capability to internally insert a waveguide path poses a big challenge from the fabrication point of view. We present a fabrication method for a 3D lattice with designed linear defects by multitilt x-ray exposures and electron-beam lithography. This combination of different lithographies has been developed to control the design and the realization of the linear defects inside the three-dimensional structure. This method has been applied for the fabrication of Nickel Yablonovite lattices with a lattice parameter of 1.8 mum and a total thickness of 15 mum, a value that allows us to achieve a full three-dimensional optical behavior as confirmed by variable angle reflectance measurements. (C) 2003 American Vacuum Society.