Urban roadside levels of benzene, toluene, ethylbenzene and xylenes (BTEX) were investigated in three typical cities (Guangzhou, Macau and Nanhai) in the Pearl River Delta Region of south China. Air samples were collected at typical ground level microenvironments by multi-bed adsorbent tubes. The BTEX concentrations were determined by thermal desorption-gas chromatography-mass selective detector (TD-GC-MSD) technique. The mean concentrations of benzene, toluene, ethylbenzene and xylenes were, respectively, 51.5, 77.3, 17.8 and 81.6μg/m3 in Guangzhou, 34.9, 85.9, 24.1, 95.6μg/m3 in Macau, and 20.0, 39.1, 3.0 and 14.2μg/m3 in Nanhai. The relative concentration distribution pattern and mutual correlation analysis indicated that in Macau BTEX were predominantly traffic-related while in Guangzhou benzene had sources other than vehicle emission. In Nanhai, both benzene and toluene had different sources other than vehicle emission. The samples collected from Guangzhou showed that BTEX had significant higher concentrations in November than those in July. Copyright © 2002 Elsevier Science Ltd.