The essential oils from four medicinal plants from Nigeria were obtained by hydrodistillation and analyzed by means of GC and GC/MS. The main constituents of the leaf and stem oils of Vernonia perrottettii Sch. Bip. (Asteraceae) were sesquiterpene hydrocarbons (92.1%) with abundance of b-caryophyllene (28.1% & 39.8%) and germacrene D (34.5% & 16.0%) in the leaf and stem oils, respectively. On the other hand, the leaf oil of Eucalyptus decaisneana Sm. (Myrtaceae) was dominated by the monoterpene hydrocarbons (90.6%) with a-phellandrene (31.1%), p-cymene (20.8%) and g-terpinene (11.7%) being present in large quantities. The oil composition of immature leaf of Hyptis suaveolens L. (Lamiaceae) revealed the abundance of b-caryophyllene (22.3%), a-phellandrene (10.6%) and caryophyllene oxide (10.3%). The compositional pattern may probably lead to the delineation of a new chemotype of this species.