5,11-Dimethyl-2,9-bis(phenylacetyl)-5,11-diazatetracyclo[18.104.22.168(2,7)90(4,9)]dodecane (2a) has been found to be a potent narcotic analgesic of unusual structure. All of the analgesic activity was attributable to the levorotatory isomer 2b which was approximately three times as potent as morphine in the rat. Removal of one N-methyl group from 2a reduced, but did not abolish, the analgesic activity. However N-allyl analogues were neither agonists nor antagonists. Replacement of one of the phenyls of 2a with a cyclohexyl group yielded an analogue with considerable activity. Structural similarities with derivatives of ethenooripavine are noted.