The effect of pressure on the melt viscosity was experimentally investigated for five polymers: polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polypropylene (PP), and low-density polyethylene (LDPE). Measurements were carried out using capillary rheometer modified to allow regulation of back pressure. To enable correction for the entrance pressure drop, two round-hole dies were used: a 1-mm diameter die of length 10 mm and an orifice die of the same diameter. For determining the pressure coefficient from the experimental viscosity data, time-pressure superposition was applied to generate a master curve to which the Carreau-Yasuda model was fitted. The resulting pressure coefficients revealed that for the polymers studied the order of the degree of the pressure dependence is as follows: PS > ABS > PC > PP > LDPE. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1076-1084, 2010