An air trajectory statistical approach was developed to estimate the relative contributions of various sources within a planning domain for a receptor site during high air pollution. The proposed approach is based on the coupling of residence time analysis and a known emission inventory. The theoretical basis of the approach is detailed. The approach was applied to investigate the relative contributions of various anthropogenic volatile organic compound (VOC) sources to the ozone formation potential of a receptor site in southern Taiwan. One hundred and ninety-seven ozone events (defined as those with an hourly ozone concentration that exceeded 120 ppb standard) over 1994--1998 were selected to undergo the residence time analysis. The VOC emission inventory was adjusted to reflect the different ozone formation potentials of the various sources by considering the source VOC profiles and the maximum incremental reactivity scales of each VOC compound. The results show that the sources that influenced the evaluated receptor site were located in northwestern coastal regions; the relative contributions of the point, line, and area sources were in the ration of approximately 5:2:3. Two districts, Kaohsiung City and Kaohsiung Hsien, were the dominant contributors of the five investigated districts. The proposed method may act as a preliminary tool to efficiently select the potential source region/category, such that mitigation and control strategies can be targeted, and/or used to guide a comprehensive modeling study.