Selected org. compds. in rain and roof runoff from a station in a domestic residence and a garden settlement were identified and quantified with GC/MS, GC/ECD, and GC/FID. More than 80 trace org. substances, which are high priority pollutants such as PAHs and phenols, were identified. Many compds. could not be identified by GC/MS in the normal scan mode, better results were obtained GC/MS-SIM. The advantage of this methodol. is that it simplifies sample prepn. procedures, avoids overlap of different peaks, and makes peak identification less complicated. A first-flush-effect apparent in elec. cond. measurements during the rain fall was caused by particle accumulation on the roof surface in dry periods. Quant. results showed that the amt. of trace org. substances in rain and roof runoff varied considerably, both in individual rain events and between different samples taken at different time windows during a single rainfall. The concn. of org. substances in the rain decreases as follows: fatty acid > phenols > chlorinated compds. This wide distribution range of the data presented is assumed to be due to the different properties of substances, the extent of air pollution, intensities of rainfalls, intervals between consecutive rainfalls, and differential adsorptivity of substances on the roof surface as well as on the submicron particles in the atm.