Orientation studies have been undertaken in uniaxially oriented drawn tapes of isotactic polypropylene, using the techniques of wide angle X-ray diffraction, polarized fluorescence and optical birefringence. The results have been interpreted on the basis of a simple two-phase model for orientation of the crystalline and noncrystalline regions. The rise in the orientation of the crystalline regions with increasing draw ratio is extremely rapid, even compared with the pseudo-affine deformation scheme. This result, taken in conjunction with the discontinuous change in the long period, supports the view that the plastic deformation involves a complete breakdown of the original lamellar structure and subsequent recrystallization of the highly oriented drawn material. Further support for this conclusion is obtained from the observation that the orientation of the long fluorescent probes, which might be expected to be constrained to the more highly oriented material, is similar to that measured for the crystalline material by X-ray diffraction.