|Beschreibung:||The study about colonization of scleractinian corals using concrete substrates (20 x 20 x 2 cm), at coral reefs of Pandan (100o 8’ 16.91” E and 0o 55’ 55.51 S) and Setan Islands (100o 22’ 51.74“ E and 1o 07’ 09.13“ S) was conducted from February 2000 to January 2002. This study also observed sexual maturation and the timing of reproduction in 16 species of adult corals from 6 families. In addition, plankton samples were used to monitor the occurrence of eggs and planulae of corals. The total number of coral colonies settled on the substrates every month, every three months (seasons), and after two year of investigations at Setan Island is greater than at Pandan Island, whereas every year sampling at Pandan Island is higher than Setan Island. The most settlements occurred during the intermediate of season I (February to April) and II (August to October) and in the beginning of the rainy season. Coral species, which settled on the substrates during the periods this study, were dominated by species from families of Pocilloporidae (Pocillopora damicornis, Pocillopora sp., P. verrucosa, and Styllopora sp.) and Acroporidae Acropora sp., Montipora aequituberculata, Montipora sp., A. cerealis, and A. verweyi) as well as unidentified species. Other coral families such as Poritidae (Porites sp.), Oculinidae (Galaxea sp. and G. fascicularis), Merulinidae (Merulina sp., and M. scrabicula), Faviidae (Platygyra sp.), and Agariciidae (Leptoseris sp.) also occurred but in lower number. The adult corals that lived in each location probably were the source of the coral colonies, which settled on the concrete substrates on the both locations. In addition, settlement occurred in both locations when surrounding corals produced eggs or planulae larvae were found in the water column.