Concentrations of uranium and thorium in seawater, sediment and some marine species taken from along the coastal areas of Malaysia were determined spectrophotometrically. The uranium and thorium concentrations in seawater were found to vary ranging from 1.80 to 4.1 and 0.14 to 0.88 mu g/L, respectively. The concentration of uranium in sediment samples was reported to range from 3.00 to 6.60 mu g/g while those of thorium were slightly lower ranging from 0.01 to 0.68 mu g/g. The uptake of uranium and thorium in marine species was found to be rather low. Similar variations in total alpha activities in samples were also observed with the total alpha activities relatively lower than the beta activities in most samples. (C) 2006 Elsevier B.V. All rights reserved.