Most of O'ahu's nearshore and beach sands are highly calcareous and of biogenic origin. The pale-colored constituent grains are the eroded remains of carbonate shells and skeletons produced by marine organisms living atop the island's fringing reefs and in the shallow waters near shore. Previous studies have shown that the tests of symbiont-bearing benthic foraminifera compose a substantial portion (up to one-fourth) of these organically produced sands. We sampled a variety of reef flat and slope habitats to obtain standing-crop data and production estimates for several sand-producing genera of reef-dwelling foraminifera. We found that modern communities of these shelled protists occur in dense numbers islandwide, reaching densities up to 105 individuals per square meter of suitable substrate in the more productive habitats. Further research on the contribution of foraminifera to beach, nearshore, and offshore sands is planned for O'ahu and neighboring islands to describe their roles in the sediment budget more completely.