We now report the isolation and structure elucidation of bengacarboline (1), a new tetrahydro-â-carboline with two indole units attached to C1 of the carboline nucleus from the Fijian ascidian Didemnum sp. Fascaplysin (2) was also isolated from the extract. Bengacarboline (1) was cytotoxic toward a 26 cell line human tumor panel in vitro with a mean IC50 of 0.9 µg/mL and inhibited the catalytic activity of topoisomerase II at 32 µM.