One year of hydrogen sulfide measurements in an urban traffic site were used to assess the importance of traffic in the overall high ambient air burden of H2S (mean annual concentration of 8 ¿g/m3). During calm nighttime hours, hourly values of H2S were correlated positively with those of CO (R2 = 0.75) and SO2 (R2 = 0.70), suggesting a common source from traffic. For the driving conditions of the measurement site, H2S automotive emissions are around 24% w/w those of SO2, while European inventories calculate these at only 2.5%. H2S annual traffic emissions, based on the existing emission inventories for CO and SO2 are calculated at 0.199--0.311 ¿ 10-3 Tg a-1 for Thessaloniki and are extrapolated to 0.030--0.0485 Tg a-1 for the EU15 countries and 2.6 Tg a-1 for Europe and Eurasia. It appears that traffic emissions make up a significant contribution to the global H2S budget.