The flow of air through compact bundles of parallel textile fibers has been studied in order to obtain values of the shape factork0for the channels through which the flow takes place. When the fibers are cylinders and the flow is parallel to their axes,k0is an increasing function of the porosity &egr;. Tables and curves showing this relationship are given. For fibers such as cotton, where the shape and size of cross section changes along the fiber length,k0changes less rapidly with &egr;. Data are given for this relationship.