The essential oils of four plant species from Nigeria have been extracted by hydrodistillation and analyzed by GC and GC-MS. The oils of Cajanus cajanwere comprised of sesquiterpenes (92.5%, 81.2% and 94.3% respectively in the leaves, stem and seeds). The major compounds identified were α-himachalene (9.0-11.5%), β-himachalene (8.0-11.0%), γ-himachalene (6.9-8.1%), α-humulene (7.1-8.7%) and α-copaene (4.5-5.6%). However, monoterpenoid compounds (81.8%) dominated the oil of Moringa oleiferawith an abundance of α-phellandrene (25.2%) and p-cymene (24.9%). On the other hand, aldehydes (52.8%) occurred in the highest amount in Heliotropium indicum, represented by phenylacetaldehyde (22.2%), (E)-2-nonenal (8.3%) and (E, Z)-2-nonadienal (6.1%), with a significant quantity of hexahydrofarnesylacetone (8.4%). The leaf and stem oils of Bidens pilosawere dominated by sesquiterpenes (82.3% and 59.3%, respectively). The main compounds in the leaf oil were caryophyllene oxide (37.0%), β-caryophyllene (10.5%) and humulene oxide (6.0%), while the stem oils had an abundance of hexahydrofarnesyl acetone (13.4%), δ-cadinene (12.0%) and caryophyllene oxide (11.0%). The observed chemical patterns differ considerably from previous investigations.