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.