BASF, one of the leading producers for polymeric foams, developed a variety of foam products over the past decades, such as Styrodur®, Neopor®, Basotect® or E-por®. The majority of these foams are generated by the physical-foaming method, that means a low-boiling gas or a volatile liquid is being dissolved in the polymer melt and serves as a blowing agent. The respective processing technologies can be divided into batch processes and continuous extrusion processes with the latter one being used for both expandable beads and rigid foam sheets. With a view to future trends, the focus points at continuous foam-processes because they allow for tailoring the properties by utilizing the interaction of formulation, process engineering and morphology control. To understand and make use these interactions, an in depth knowledge of the viscosity as a function of blowing-agent formulation, content, and process parameters is required. Furthermore, optimization of existing foam-processes and reliable dimensioning of new extrusion-foam plants requires quantitative understanding of the rheological behaviour of gas-laden polymer melts. However, regarding novel material systems, such as gas-impregnated polymer blends or polymer melts with complex blowing-agent mixtures, the required rheological data is often not available and cannot be measured by offline-methods. To overcome these drawbacks, a novel high-pressure inline-rheometer has been developed, which is able to capture the required rheological data at realistic process conditions. With the novel inline-device the viscosity-function of gas-loaden polymer melts could be detected at pressure levels up to 400 bar and, thus, complement the pressure-limited offline methods.