Intensive measurements of chemical species were conducted during February March, 1994 at Kenting, which is at the southern tip of Taiwan, in accord with the Pacific Exploratory Measurements in the western Pacific ocean (PEM-West B) experiment. In general, frequent outbreaks of cold polar air mass dominated the synoptic weather pattern, which was led by a fast moving cold front and followed by steady northeasterly winds over the Taiwan region. There was frontal passage only eight times, each taking about 48 hours to complete. Steady northeasterly winds prevailed during most of the study period and were associated with a negligible diurnal variation of the chemical species. The median level of ozone, CO, and SO2 in the northeasterly wind was 45.7, 198, and 0.08 ppbv, respectively. Dramatic changes in the levels of O3, CO, and SO2 occurred during each frontal passage, which was characterized by a drop in the surface pressure, a swift change in the wind direction, and a reduction in the wind speed. The ozone level dropped from 40--55 ppbv to about 6--15 ppbv at 12--18 hours after the time of the surface pressure minimum, and then it took about 6--18 hours to be restored to its original level. In the meantime, the levels of CO and SO2 also decreased in the beginning but increased dramatically up to 400--556 ppbv and 1--9.51 ppbv, respectively, right after the frontal passage. Later on, their concentration dropped back to the original steady level in a northeasterly wind. ¿ 1997 American Geophysical Union