The specified method is applicable both to styrene homopolymers and to butadiene modified polystyrene. It may be used also for the simultaneous determination of other volatile aromatic hydrocarbons in polystyrene. Dissolution of the polymer sample in chloroform or dichloromethane. Precipitation of the polymer by the addition of methanol and injection of a small volume of the remaining solution into a gas chromatograph with flame ionization detector and recorder. The solvent shall contain a known amount of n-butylbenzene as an internal standard for quantitative evaluation.