Finite-element modelling is used to simulate the response of atherosclerotic arteries to a balloon angioplasty procedure. Material properties for the normal wall are derived from experimental data, and the properties of the plaque are varied over a wide range. Comparison with experimental data shows that the normal arterial wall can be appropriately modelled using a hyperelastic material definition. Large strain, non-linear analysis was used to simulate the dilatation of three typical plaque configurations by an angioplasty balloon. Stress contour plots are presented for each configuration. Results show good agreement with previous histologic studies.