We hypothesize that mechanical factors within heterogeneous atherosclerotic human arteries are important, either as primary determinants of plaque stability or as influences on relevant cell activity. We developed an experimental system to measure the finite deformation of diseased human arterial cross sections at physiologic pressures. Strains are calculated using interpolation functions. The distributions of lipid, calcified, healthy and fibrous tissue are measured using differential staining and light microscopy. The presence of matrix metalloproteinase 1 is also quantified. Histologic features and deformations are incorporated into a plane stress finite element model and tissue constituent material properties, stresses and strain energies are determined using an optimization procedure. Results show correlation of stress and strain distributions with histologic make up of the tissue and with staining for matrix metalloproteinase (MMP-1).