There are provided internally cross-linked, stable polymeric materials, in the form of substantially spherical particles, each particle consisting essentially of a single macromolecule. They have the unusual property of being soluble or dispersible in a liquid medium without significantly increasing the viscosity of the medium, rendering them potentially useful in imaging applications such as ink jet printers. They can be prepared by dissolving polymeric material in a solvent system to form a solution of the polymeric material at a concentration therein of less than the critical concentration for the polymer, causing the polymeric material to contract into an approximately spheroidal conformation in solution, cross-linking the polymeric material in solution in said spheroidal conformation so assumed, and recovering stable, cross-linked approximately spheroidal polymeric particles from the solution.