1,2-Bis(1H-indol-3-yl)ethane-1,2-dione (1), a bisindole alkaloid, was isolated from the marine sponge Smenospongia sp. The known compounds indole-3-carbaldehyde (2), 6-bromoindole-3-carbaldehyde (3), and tryptamine (4) and mixtures of the (Z/E) isomers of 6-bromo-2'-demethylaplysinopsin (5a/5b) and 6-bromo-3'-deimino-2',4'-bis(demethyl)-3'-oxoaplysinopsin (6a/6b) were also isolated.