Operating data for several slurry pipelines in the Alberta oil sand industry have been sampled and interpreted with the assistance of the Saskatchewan Research Council (SRC) Two-Layer model. The slurries are described within the industry as normal tailings, dense tailings, or oil sand slurries. All are of the so-called heterogeneous or settling slurry type. The pipelines considered ranged in diameter between 0.483 m and 0.737 m. The useful operating data included water and slurry pressure drop measurements recorded during periods in which velocities and densities were nearly constant. The data reveal that the friction is often higher than predicted by the SRC Two-Layer model, which makes no allowance for the effect of large particles (>50 mm) which are known to be present. This friction increment appears to be higher when the pipelines have sections with upward slopes.