The current study reports on a series of ultrafiltration experiments using newtonian and non-newtonian fluids (pectine, xanthan and polyacrylamide solutions). For non-newtonian pseudoplastic fluids, the shape of the plot of flux versus log(bulk concentration) is different to the linear decline in flux which would occur throughout. Moreover, we observed that the axial velocity exponent decreases with increasing bulk concentration. An empirical equation for the laminar mass transfer coefficient of a pseudoplastic fluid has been proposed which includes a Sieder and Tate type correction factor. The equation is a tool for understanding the decrease in axial velocity exponent with increasing bulk concentration. However, a comprehensive numerical model is necessary to get better agreement between observed and predicted axial velocity exponent and permeate flux.