Friction losses in 0.2-0.3 m i.d. pipelines were investigated for three coarse sands with mass median particle sizes of 0.6-0.7 mm and size distributions of 1.4, 5.4 and 27.3, respectively, when expressed in terms of the ratio of particle diameters 85 to 15% by mass finer. The partially-stratified friction loss model proposed by K.C. Wilson, G.R. Addie and R. Clift, Slurry Transport Using Centrifugal Pumps, Elsevier, Oxford, 1992 [1] predicted the observed friction losses reasonably well at volumetric concentrations of 12-15% for velocities of practical interest. Good agreement was found for concentrations of up to 31% for sand with the intermediate distribution. However, predictions for the narrowest sand underestimated friction losses at higher concentrations of 26-31%. Friction losses for the broadest sand were overestimated markedly at concentrations of 28-39%. With these two sands, observed losses did not increase linearly with concentration, in disagreement with model assumptions. The different mechanisms involved are discussed in light of results demonstrating how particle size distribution, content of particles 0.1-0.5 mm in size, and concentration affect friction losses. The flow conditions discussed here correspond to velocities that clearly exceed those for which there are risks of deposition at the bottom of the pipe.