The structure of hircinol, a phytoalexin isolated from Loroglossum hircinum has been established as 2, 5-dihydroxy-4-methoxy-9,10-dihydrophenanthrene. This phytoalexin, the second to be identified in the Orchidaceae, is less effective than orchinol, and its isomeric co-metabolite, loroglossol, 5-hydroxy-2,4-dimethyoxy-9,10-dihydrophenanthrene, is inactive. © 1973.