A method for the determination of chlorodiphenyl (54% chlorine) in particulate matter, involving the collection of a known volume of air through a cellulose membrane filter, extraction with petroleum ether and its analysis by electron capture gas chromatography is described. The area of the sample peaks is determined and compared with areas obtained from standards. The probable useful range of this method is 0.05 to 1.5mg per cubic meter for 100 liter samples. Validations were made between 0.322 to 1.255mg per cubic meter. It was suggested that if higher concentrations must be used, sample volumes should be smaller since the upper limit of the range is dependent on the collection efficiency of the filter. The coefficient of variation for the total analytical and sampling method was 0.063 which corresponds to a standard deviation of advantages and disadvantages, description of apparatus, reagents, procedure, analysis of samples, calibration and standards and calculations were described for this method.