Separation of polyvinylpyrrolidone, a water-soluble polymer of neutral charge, by high osmotic pressure chromatography (HOPC) is presented. HOPC, suitable for preparative separation of polymer by molecular weight, has been applied to various organic-soluble polymers. We demonstrate here that HOPC can also separate water-soluble polymers and is capable of separating fractions of narrower polydispersity compared to preparative gel permeation chromatography (GPC). Typically fractions with a polydispersity index (PDI) of 1.4-2 were generated from broad-distribution polymers (PDI similar to 5) in significant quantities from a single separation. By multi-stage separation, standard-grade fractions were obtained. Single- and multi-pass fractions were characterized by both GPC with narrow-standard calibration and GPC in tandem with a multi-angle laser light scattering detector.