The sesquiterpenes 7-hydroxycalamenene and (+)-calamenene isolated from Eremophila drummondii have been interrelated. The crystal structure and absolute configuration of the p-bromobenzoate of 7-hydroxycalamenene, C,,H,5Br0,, has been determined ; crystals are orthorhombic, space group P2,2,2,. unit cell dimensions a = 9.471 (5). b = 11.469(5), c = 18.253(7) A, for Z = 4. These results show that both sesquiterpenes have the (1 R.4R) -configurations and resolve the present confusion on this point.