In this research, the effects of the materials and the processing conditions on the cell morphology of foamed PVC/wood-fiber composites were studied with a view to establishing their process-structure relationships. Each step of microcellular PVC/wood-fiber composites processing is addressed, including the surface treatment of the wood-fiber, mixing of polymer and wood-fiber, manufacture of the composites, the saturation of the composites with gas, microcellular foaming of the composites, and characterization of the cell morphology. The cellular morphologies of the foamed PVC/wood-fiber composites are a strong function of the content of plasticizer and the surface treatment of wood-fiber as well as the gas saturation and foaming conditions.