The design of expandable polystyrene foam buffers, used as protective packaging for a range of goods, is by and large steeped in heuristics because the design procedures have not been formalized. This paper discusses the application of Taguchi＇s Method of Parameter Design to the determination of the key design parameters of expandable polystyrene foam end cap buffers. An L-18 orthogonal array was adopted for the planned experiments. The eight design parameters considered critical in the design of the cushioning buffers were product centroid-to-buffer centroid distance, cushioning area, buffer thickness, wall thickness, material density, rib configuration, rib width, and rib spacing; of these, only buffer thickness, wall thickness and buffer density were found to be significant at a 99% confidence interval. The height of the ribs, being the difference between the buffer and wall thicknesses, is the single most important factor. The buffer cushioning area was found to be not as important as its distribution over the entire load-bearing area and the buffer configuration. The buffers were designed in Unigraphics II, and the post-processing of the NC part program for machining on the Hamai vertical machining center. The impact shock testing of the end cap buffers was conducted on the Lansmont Model 65/81 Shock Test System.