The use of TBT-based antifouling paints is not regulated in Indonesia but, since they are not used on small vessels, large commercial ships are the major source of TBT contamination in the marine environment Measures of imposex in Morula spp and Thais spp indicate that ports and adjacent areas are the most severely polluted places The effects of imposex in Indonesia have, however, been less dramatic than those described in Europe and elsewhere Even after 30 or so years continuous exposure to TBT, there are still populations of muncids in ports Imposex was mostly mild or absent at open coastal sites, where there was little boating activity, suggesting that the open seas are largely free of contamination at biologically significant levels There was some expression of imposex in whelks collected from fishing ports where there were no obvious sources of TBT