In this study melt rheological behavior of lactose-filled polyethylene glycol (PEG) composites as a low melting polymeric carrier for controlled release drugs was investigated using a capillary rheometer. The effect of lactose concentration and process variables such as temperature and ram speed on the flow behavior of PEG has been studied. The composites were found to be shear thinning in behavior when extruded, and the results were well described by power-law model in each case. Stronger shear thinning behavior was observed by raising the filler concentration and decreasing the temperature, while the flow index has been decreased. In all compositions a significant increase in shear viscosity was found by an increase in the filler content. In fact, shear viscosity increased linearly by weight fraction of filler, but there was a dramatic increase after the filler content raised above 20 wt% of lactose which might be the result of the strong interaction among filler particles. Furthermore, decreasing the process temperature resulted in an increase in shear viscosity, and the temperature dependence of shear viscosity decreased as the shear rate increased. The extensional viscosity of composites was calculated in each case. The results showed that the ratio of the extensional viscosity to shear viscosity was in the range of 500-1200.