In food technology, cereals based on starch melts are often manufactured by the process of extrusion cooking. To characterize the rheological behavior of the starch melt during the process, a new inline rheometer was developed. Special features of the rheometer are the adjustable pressure loss to avoid reactions to the starch stress in the extruder and variable measuring geometry, and therefore, shear rate during extrusion. Using this inline rheometer, it was possible to correlate the inline determined flow functions with the molecular weight distributions of the starch.