If expandable Polystyrene (EPS) was a human being, it would have reached its retirement age these days. Invented and introduced in the early 1950s, it has served for more than 65 years as an efficient and versatile material for thermal insulation and packaging. But even after such a long adolescence there is still room for further improvement. There are two basically different ways to produce EPS beads. The traditional route is the autoclave process. In this case the blowing agent, usually pentane, is added in the final phase of the polymerization. The product is obtained in form of white pentane-loaded unexpanded spheres of approx. 1 mm diameter. The alternative is to use an extrusion process starting from general purpose polystyrene (GPPS). In the second half of the extrusion process the products are thoroughly homogenized and cooled. It is important to ensure that there is a single-phase mixture at the outlet of the extruder. Further cooling may be carried out in a subsequent melt cooler, which is a specially designed static mixer. Finally the EPS-beads are obtained by underwater pelletizing. The pelletizer is designed to work with pressurized water in order to prevent the beads from premature expansion at this stage. Properties and performance of extruded EPS are comparable to autoclave EPS in every respect. However, the extrusion process is in our view far more flexible and in the end more economical as it allows simultaneous incorporation of any additive and also the use of recycled PS. Leistritz has carried out studies in co-operation with Fraunhofer ICT. Results have shown that there is potential for higher cost efficiency in the extrusion process. EPS – 65 years and still going strong. The paper provides a view into the complex extrusion process of EPS manufacturing: From the complete production system consisting of both hardware, a high performance extruder with all its ancillaries to “software”, i. e. state-of-the-art EPS recipes and process know-how.