Fuscol and the related fuscosides are diterpenes isolated from the Caribbean gorgonian Eunicea fusca, which exhibit potent anti-inflammatory activity with a selective action against leukotriene production in murine models. This report describes the isolation and characterization of the diterpene cyclase product leading to these natural products. The cyclase product has been assigned the trivial name eunicene A and was identified through a radioactivity-guided isolation. Additional biosynthetic experiments conducted by incubating a cell-free extract of E. fusca with 3H-labelled metabolites confirmed the involvement of this unsaturated hydrocarbon in the production of fuscol and fuscosides.