Aerosol samples from a forest site were collected on glass fiber filters, and particulate bound organics were analyzed by a thermodesorption GC/MS procedure. A conventional GC injector was modified to enable the insertion of loaded filter samples without disarranging the GC-system. Seven commercial glass fiber filter types were tested for performance with regard to sampling and analysis requirements. Sixty-six substances were detected in aerosol samples, 40 organics, mainly n-alkanes, phthalic acid esters, fatty acids, fatty acid esters, n-alkane nitriles and polycyclic aromatic hydrocarbons (HCs) were identified. Comparative measurements of samples collected at an urban site and in flat showed only small differences for the ratio of the main constituents identified. © 1990.