Studies conducted at Kwajalein Atoll (9°N; 168°E) in early 1988 reveal that marine organisms are commonly rafted into the area on drift pumice, drift wood and other flotsam. Coralskeletons on pumice provide the most useful quantitative data because they persist after rafted motile organisms have departed and rafted sessile forms have decomposed or been scavenged. The estimated minimum number of pumice fragments carrying corals into Kwajalein Atoll during its geological history is on the order of 109, with a more realistic estimate in excess of 1011. The estimated number of coral colonies rafted into the atoll would probably have to be increased several-fold if rafting on floating organic materials such as wood, charcoal, nuts and seeds could be determined. In the present study, a typical sample of beached pumice from Kwajalein Atoll contained 103 coral colonies per m3 of bulk pumice fragments. Major pumice rafting episodes frequently result from volcanic eruptions. Estimates based on the observed K wajalein coral fouling rate and literature values for drift pumice production suggest that 105 colonies could be rafted through the tropics by the smallest reported pumice-producing events and up to 1012 colonies for large events. In the present study, most of the rafted corals that were recovered belong to species of the genus Pocillopora, but speccics of Porites and Millepora were also collected. Analysis of surface-current data and reported drift patterns for pumice, logs, drift bottles and wrecks suggests that movement of rafted corals and drifting larvae is predominantly from peripheral areas of low coral-species diversity into centers of high coral diversity. Coral diversity centers might be viewed as areas of coral species accumulation rather than centers of coral species origin.