Detailed profiles of dissolved and particulate ²³⁴Th, ²¹⁰Pb, and ²¹⁰Po activities at three stations in the Hung-Tsai Trough off south western Taiwan were determined. The total ²³⁴Th activ ity is 20 ~ 25% deficientfrom its secular equilibrium in the entire water column. Except for an evident excess of ²¹⁰Po at some depths in the mixed layer and in the pycnocline layer, total ²¹⁰Po activity is also lower than total ²¹⁰Pb activity. As a result of atmospheric deposition, ²¹⁰Pb is about 25% in excess of its parent, ²²⁶Ra, through out the water column of the Hung-Tsai Trough. The ratios of the distribution coefficients of ²³⁴Th, ²¹⁰Pb, and ²¹⁰Po show that the order of particle affinity is Po > Th ~ Pb in the mixed layer and bottom layer, whereas the order changes, due to particlere generation, into Th > Pb > Po in the pycnocline layer of the Hung-Tsai Trough.