Increasing threats to deep-sea corals highlight the need to expand knowledge of these taxa so that conservation measures can be developed. The present study focused on the reproductive patterns of the deep-sea solitary coral Flabellum angulare. A series of samples (n = 398) collected in 2006-2008 in the northwest Atlantic at depths of 925-1,430 m revealed that gametogenesis was synchronous among males and females and fluctuated seasonally. Initiation of gamete synthesis was estimated to be in August-September and spawning in June. Further analysis and daily monitoring of 30-60 individuals maintained in a flow-through mesocosm showed that gamete release occurred in March-June with a peak in May. Release of oocytes coincided with rising seawater temperatures and high deposition rates indicative of elevated water column productivity. Oocytes (900-1,200 mu m diameter) were released through the oral cavity, generally in bundles of 3-5 surrounded by mesenterial filaments and attached to a thread (30-50 mm long). As oocytes became free in the water column, ovulation occurred followed by fertilization. Eggs/embryos initially remained on the tentacles of the spawner before either falling onto the substratum or floating to the surface. The embryos developed into planula larvae measuring 2-3 mm in length within about 24 h. Together, these findings shed new light on the strategies used by deep-sea corals to maximize their reproductive success.