Observations of chlorophyll a concentration and phytoplankton assemblage were conducted during the summer of 1990 on 19 stations along two parallel transects across the Kuroshio Current front off the northeastern coast of Taiwan. The 0-100m seawater chlorophyll a content varied between 8.63 and 41.80mg·m-2 in August and between 8.88 and 94.70mg·m-2 in September. High nitrate content, low temperature, high salinity and high chlorophyll a concentrations were observed at the stations along the front. The vertical distribution of chlorophyll a was characterized by a shallower subsurface maximum of between 0 and 25m in the stations associated with the upwelling, while those of the non-upwelling stations were between 50-75m. Diatoms, Skeletonema costatum in August and Thalassionema nitzschioids in September, dominated the upwelled surface water because significant amounts of nutrients are supplied to surface or near-surface waters.