Living corals were collected at Galle, Ceylon, and at ten localities in the Maldive Islands. Fiftyfive coral heads, 10 of the family Pocilloporidae and 45 of the family Acroporidae, were examined for decapod commensals. Shrimp found exclusively in Pocillopora, together with frequency of occurrence, if more than once, were Alpheus lottini (9), Harpiliopsis beaupresi (5), H. depressus (5), H. spinigera, Philarius sp. (probably gerlachei, Fennera chacei, and Tkor maldivensis. Crabs found exclusively in Pocillopora were Trapezia cymodoce (8), T. ferruginea (6), T. aff. wardi (3), Domecia hispida (3), Trapezia areolata, T. aff. danai, T. aff. maculata, T. aff. tigrina, and Cymo quadrilobatus. Shrimp found exclusively on Acropora were Jocaste japonica (17), Coralliocaris superba (3), Jocaste lucina (2), Coralliocaris graminea (2), C. nudirostris, C. venusta, and Periclimtnes lutescens. Crabs found exclusively or Acropora were Tetralia glaberrima (33), T. heterodactyla (19), Cymo deplanatus (13), C. melanodactylus (4), Domecia glabra (6), Crabs found in Ceylon but not in the Maldive Islands were Trapezia aff. tigrina, T. areolata, and Cymo (?) on Pocillopora and Cymo deplanatus on Acropora. Shrimp found in the Maldive Islands but not in Ceylon were Philarius sp. (probably gerlachei), Harpiliopsis spinigera, Fennera chacei, and Thor maldivensis on Pocillopora and Coralliocaris nudirostris, C. superba, C. venusta, Periclimtnes lutescens, and Jocaste japonica on Acropora. Crabs found in the Maldive Islands but not in Ceylon were Trapezia aff. danai, T. digitalis, and T. aff. maculata on Pocillopora and Cymo deplanatus and C. melanodactylus on Acropora. In the Maldive Islands Tetralia glaberrima and T. heterodactyla occurred in the proportion of 2:1, Harpiliopsis depressus and H. spinigera in the proportion of 3:1, and Jocaste japonica and /. lucina in the proportion of 8:1. Each head of Acropora usually supported a pair of Tetralia: either T. glaberrima or T. heterodactyla (19 times) or both (5 times). The occurrence in the same coral head of mated pairs of both, and of multiple numbers of both congeners of shrimp, was evidence of their specific identity, formerly in doubt.