Abstract The aim of this work is to study the effect of different types of chemical and biological dispersants used for crude oil spill treatment. The dispersing efficiency of the different dispersants on the crude oil was determined for selecting the most effective one. The basic properties of crude oil participating in the efficiency of dispersion process as viscosity, pour point, wax content, asphaltene content, resin content, etc. were determined. Also the nature of the different dispersants on the dispersing process, studied by FT-IR analysis, showed the presence of the same effective functional groups but in different ratios. The hydrocarbons types distribution of crude oil undispersed and undispersed parts were used as a marker for the degree of dispersion and/or biodegradation. The lowest values of undispersed saturate indicate the highest degree of dispersion or biodegradation. The lower normal alkanes are much more dispersed than the higher ones. The enzyme showed a moderate efficiency for dispe...