This chapter discusses the flow of solid particles transported by a liquid in pipelines, namely, slurry pipelines. For simplicity, the discussion will focus on horizontal or nearly horizontal pipes with particles suspended by the liquid. Understanding this mechanism of particle suspension helps comprehend what happens to pipe flows of suspended solids – be it for solid-liquid mixture (slurry flow) or solid-gas mixture (pneumotransport). Whether a pipe flow of solid-liquid mixture is to be treated as pseudohomogeneous or heterogeneous depends on the variation of solids (sediment) concentration in the pipe. Wasp's approach has proved satisfactory for predicting pressure drops along some commercial coal slurry pipelines. The Wasp approach and most other approaches for predicting the headloss in slurry pipelines assume negligible attrition of particles during pipeline transport. Slurry pipelines are widely used in many fields and by many industries for transporting bulk solids, which can be exposed to water in a pipe without damage or detrimental effect.