A wound dressing composition comprising a partially cured polyurethane fluid. The composition can be injected directly into a wound, where it cures to form a wound filling dressing. Also provided is a wound dressing comprising such a composition. Also provided is a kit for the preparation of such wound dressings, the kit comprising (a) a polyurethane prepolymer; and (b) a curing agent for the polyurethane prepolymer. Preferably, the polyurethane components comprise reaction products of a diisocyanate with castor oil or a related ester of ricinoleic acid or its derivatives.