Abstract: Zooplankton samples collected from eight stations around Pulau Redang, Terengganu, Malaysia were use for measure the concentration activities of 210Po and 210Pb using Alpha Spectrometry. Mean activity in zooplankton tissue for 210Po [364.67±21.00 Bq kg 1 (dry wt.)] was much greater than 210Pb [93.67±6.83 Bq kg 1 (dry wt.)] with ranging ratio of 210Po/210Pb from 3.46 to 4.71. These fluctuated may be related to the feeding habits of zooplankton and daily biological processes occurred in water column.