Samples of surface sediment of St. Johns River Basin were collected, extracted and their aliphatic hydrocarbons (AH) were determinated quantitatively and qualitatively by GC-FID and GC-MS Techniques, were used to characterize the (AH) hydrocarbons homologous and biomarker compounds.The sediments contained high organic matter content, while the hydrocarbons AH represented ٠,٣٥-٢,٧٢٪ of the total organic matter (TOM) found in sediments.