Crossflow filtration of various latex dispersions stabilised by polyvinyl alcohol and anionic surfactants and with added hydrophobically modified water soluble polymers was studied. New data on permeate Bur rates and rejections of the latex and polymer components are presented. Holding other parameters constant it was found that the pseudo-gel concentration was dependent on the latex particle sizes and the composition of the solution, and that microfiltration membranes could be used to either concentrate or fractionate the feed. For some dispersions the steady state permeate flux shows a maximum when plotted against log(feed concentration), indicative of a change in the dominant filtration mechanism as concentration is increased. At low water soluble polymer concentration aggregation of the latex occurs, slowing the rate of permeate flux decline; at high concentrations polymer in solution deposits onto the membrane surface and causes rapid flux decline.