Radiolarian assemblages comprising 208 taxa were collected from the PARFLUX E sediment trap experiment at a pelagic station in the western tropical Atlantic. Their diversity is among the greatest ever reported for a living community. The settling flux rate of individual skeletons was on the order of 16 × 103 to 24 × 103 shells/m2/day. The species composition of the radiolarians in the sediment traps changed significantly between 389 and 988 m depth. We attributed this change to the input of nassellarian populations dwelling in aphotic deep water. The majority of radiolarian shells settle singly, and apparently reach the sea floor without substantial modification to the species composition and standing stock. The percentage of fragmentation counts of Pterocorys suggests that slow dissolution of radiolarian shells begins during the descent through the upper water column prior to reaching the bathypelagic zone.