In the last decade a number of chemically fixed, soft tissue based bioprostheses have become commercially available. Chemical fixation of these materials changes a number of their physical and chemical properties. Quantitation of these effects has been difficult because of: anisotropy of the biopolymers, variable composition of the materials, and sample size and configuration limitations. Collagen tape, made from reconstituted collagen, has been chosen as a model material because it alleviates many of the aforementioned problems. Its constituent fibers are homogeneous and unidirectional. The cross-sectional area is constant. Thus, the resultant uniaxial tensile stress-strain relationship is reproducible to allow for systematic parametric studies. Results are presented for the change in tensile properties of the collagen tape as a function of exposure time to glutaraldehyde fixative. These properties are described by the equation: sigma = A (eB epsilon-1) The tensile properties of fresh and fixed pericardial tissue were also tested and corroborative results were found.