An alternative view of the theology of semi-crystalline polymers is presented, based on suspension theory. The results in the linear viscoelastic strain regime are in accordance with experimental measurements, spanning the properties of the amorphous and crystalline phases as crystallization proceeds. Unlike some other theories, no change in the relaxation times with crystallization is predicted, especially at low crystallinity, which is in reasonable accord with experimental measurements. Slow shearing and oscillation experiments are shown to be compatible with the idea that strain is a crucial factor in increasing crystallization rates. Some non-linear generalizations are indicated. (C) 2003 Elsevier B.V. All rights reserved.