RESUMEN
The nature and seasonal distribution of hydrocarbons were studied in Ondo coastal region in Western Nigeria. The petroleum hydrocarbons were screened by gas chromatography with flame ionization detector (GC/FID) and gas chromatography-mass spectrometry (GC-MS). Complex series of compounds were identified. The overall molecular compositions obtained were characteristic of petrogenic origin with very little biogenic input. The concentrations of two important polycyclic aromatic hydrocarbons (PAHs); phenanthrene and anthracene exceeded the threshold level where adverse effects on biota would occasionally occur; a conclusion suggested to be clarified by site-specific studies on resident organisms. The study is useful for ecological risk assessment in the context of contaminant input, nature, pattern and trend.