Tanzanene (l), a spiro benzopyranyl sesquiterpene, was isolated from the rootbark of Uvaria tanzaniae Verdc. and its structure was determined by high-resolution NMR. The molecular structure of tanzanene can be thought of as a cycloaddition product of alloaromadendrene (2) and the quinone methide of o-hydroxytoluene (6-methylene-2,4-cyclohexadien-l-one, 3). The known dihydrochalcones uvaretin, diuvaretin, chamuvaretin, and isotriuvaretin were also isolated from the same plant.