Experiments were conducted on laminar Row of non-Newtonian fluid through a packed bed of low column to packing particle diameter ratio (3.8) to elucidate the wall effect on pressure drop and mass flux. Carboxy methyl cellulose (CMC) at different concentrations was passed through the packed bed and the pressure drop was measured at different CMC concentrations and flow rates. It was found that the pressure drop increases with the increase in CMC flow rate. The pressure drop also increases with the increase in CMC concentration for a given Row rate. The friction factor is plotted against Reynolds number and the data for different CMC concentration are found to be scattered around a line expressed as f = 1.03/Re-0.87. The tri-regional model of Cohen and Metzner [1] predicted correctly the mass flux in the packed bed at different pressure drop values and CMC concentrations with parameters KD (related to pore geometry) value of 1.5 and L-e/L (related to effective path length) value of 1.2, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.