Ultraviolet absorption spectroscopy, has an immense potential for characterization of aromatic hydrocarbons in distillate petroleum fractions. The second derivative ultraviolet spectroscopy has improved the understanding of complex aromatic structures, such as polynuclear aromatics, which are present in gas oil fractions. Normal and second derivative ultraviolet spectroscopy of gas oils and their separated fractions are discussed in detail and conclusions are drawn regarding mono-, di-and polynuclear aromatics in various gas oils.