Based on the results of an environmental investigation program, carried out on an oil production field at Brazilian Northeast, a contamination diagnosis was made. The field was contaminated by crude oil and saline production water and the use of in situ electrokinetic bioremediation techniques in situ were suggested for the remediation of the contaminated site. The analyzed soil is a very humid clayey silt, with high plasticity, high electrical conductivity, low hydraulic conductivity, low density, large buffering capacity and high cation exchange capacity. The soil is rich in organic matter and poor in nitrogen. The removal of the contaminated soil for ex situ treatment is not advisable in contaminated studied area due to the restrictions imposed by local environmental authority, as well as operational impediments caused by the presence of vegetation and flooded conditions. After the diagnosis a program of laboratory tests. was carried out on soil from the location in an electrical cell which was developed for this purpose. The study showed the feasibility of injecting nitrate and ammonium to this kind of soil, though the injection of phosphorous did not prove to be successful. It is recommended to control variations changes in pH, caused by the application of electrokinesis, in order not to harm the biodegradation process. (c) 2007 Published by Elsevier B.V.