Orthogonal, interconnected inorganic and organic one-dimensional nanostructures have been fabricated by parallel self-assembly on the Si(100) surface and investigated using room temperature ultrahigh vacuum scanning tunneling microscopy. In particular, bismuth nanowires were self-assembled on the clean Si(100)-2 x 1 surface perpendicular to the Si dimer rows, followed by hydrogen passivation of the surrounding Si surface. Styrene molecular chains were then self-assembled on the H-passivated Si(100)-2 x 1 surface to intersect perpendicularly with the Bi nanowires. This general approach can likely be applied to the wide range of inorganic and organic species that spontaneously form one-dimensional nanostructures on the Si(100) surface.