Kaohsiung is a densely populated harbor city, in which the density of motor vehicles is also high. Since the temperature and sunlight is also relatively high in Southern Taiwan, tending to transform ambient volatile organic compounds to ozone thus causes high ozone events. This study measured the concentrations of 63 hydrocarbon (HC) species from C2 to C15 simultaneously at the Nan-Chie and Hsiung-Kong sites in Kaohsiung city during the morning (07-10), the afternoon (13-16), and the evening (18-21) periods on three successive days in winter 2004. Results show that the most abundant species of Kaohsiung¡¦s air is toluene (43.01-60.95 £gg/m3), followed by i-pentane, 1,2,4-trimethylbenzene, benzene, n-butane, propane, and acetylene, in the range 9.55-16.93 £gg/m3, while the concentrations of halocarbons is 0.17-4.12 £gg/m3. Alkanes (44.7-45.9%) represent the largest proportion of the total HC, followed by aromatics (35.4-36.8%), alkenes (10.5-10.9%) and halocarbons (3.6-3.9 %). The OFP (ozone formation potential) of HC species were evaluated based on the MIR (maximum incremental reactivity). Results show that aromatics (45.9-54.3%) represent the largest proportion of the OFP, followed by alkenes (17.7-37.5%), and alkanes (16.5-23.6%). The results from the factor analyses show the major sources of ambient HC in Kaohsiung city are the vehicle exhausts, industrial processes, solvent evaporations, combustion exhausts, and petrochemical processes.