In order to determine the relative aging status ofupwelled or vertically mixed water in the northern Taiwan Strait, a recently developed method of calcularing the degree of nutrient consumption (DNC) was employed. Upwelling was detected at a water depth of about 75m in summer. Bottom waters in the aphoric zone and newly-upwelled waters in the euphoric zone were found to be low in terms of their DNC. In general, a low DNC was noted alongside the other traditional upwelling indicators, such as lower temperature and degree of oxygen saturation, but higher salinity, apparent oxygen utilization, nutrient contents and chlorophyll-a. Enhanced vertical mixing,but without an apparent upwelling signal, was detected near the same location in winter.