The volatile constituents identified from the leaves of two Nigerian plants are being reported. The oil samples were obtained from the studied plant species by hydrodistillation using a Clevenger apparatus and then subsequently analyzed for their constituents by gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC/MS). The quantitatively significant constituents of the leaf oil of Cassia alata (Linn.) Roxb., (Fabaceae) were 1,8-cineole (39.8%), β-caryophyllene (19.1%) and caryophyllene oxide (12.7%). Limonene (5.2%), germacrene D (5.5%) and α-selinene (5.4%) constituted the other significant compounds present in the oil. The sunflower oil, Helianthus annuus L., (Asteraceae) was rich in α-pinene (16.0%), germacrene D (14.4%), sabinene (9.4%) and 14-hydroxy-α-muurolene (9.0%).