Gives the procedure to be used for the determination of the composition (curing-agent/catalyst, modifier, resin, reaction products) of the soluble components of thermoset systems with or without reinforcement in the uncured state using High Performance Liquid Chromatography (HPLC). Also applies to: sizing systems; fibre reinforced matrix systems (such as prepreg); neat resin systems (such as film adhesives, laminating systems and components such as epoxy resins and hardeners.