Ordered arrays of collagen microfibrils form rapidly and spontaneously from a solution of monomers deposited onto a mica substrate. These arrays are well-ordered and apparently continuous over the entire substrate. Correlated atomic force microscope images and Laué diffraction patterns indicate that the protein alignment and microfibril formation is controlled by the crystal orientation of the mica substrate rather than fluid flow or drying effects. This surface-induced mechanism allows for immediate, robust, and reproducible pattern formation.