In an attempt to characterize the concentrations of ambient volatile organic compounds (VOCs) and their diurnal variations, a sampling campaign was initiated between March 24 and April 14,2011. Davutpasa Campus of Yildiz Technical University (Istanbul, Turkey) was selected as the sampling site. Forty-five VOC species were sampled during day-and night-time hours, forty-three of which were successfully quantified in ambient air. The other two (2,3,4-trimethylpentane and 1,3-diethylbenzene) were not detected in most of the samples. The measurement results indicated that toluene was the most abundant species in ambient air, followed by hexane. The concentrations of toluene and hexane ranged from 2.43 and 0.29 μg.m -3 to 135.7 and 116.3 μg.m -3, respectively. The ratios of day-time to nighttime concentrations of species were also investigated. The highest ratios were found for VOCs of industrial origin, while biogenic VOCs showed a relatively constant and low concentrations. The results from the measurements were also compared to those from previous studies. It was shown that Istanbul was one of the least polluted cities in world in the aspect of benzene, toleuene, ethylbenzene, m-,p-,oxylenes and hexane, although the sampling site was heavily surrounded by industrial zones and road with high traffic loads. © by PSP.