The inhibiting effect of certain basic and non-basic nitrogen compounds on the hydrodesulfurization of dibenzothiophene, at conditions commonly used in the hydrotreatment of diesel feedstocks, has been experimentally determined. Nitrogen compounds studied herein are indole, indoline and o-ethylaniline. The inhibition behavior of these compounds is highly non-linear, showing strong inhibition at concentrations as low as 28 ppm (as nitrogen). The inhibiting effect of the non-basic compound, indole, was found to be comparable to that of the basic compounds, indoline and o-ethylaniline, although indoline and o-ethylaniline show a slightly higher inhibiting strength than their parent compound, indole. This behavior suggests that the coverage of active sites by nitrogen compounds is established on the early stages of the reaction and remains nearly constant throughout the experiment, and shows that their inhibiting behavior is due to a strong initial adsorption of the nitrogen compound and a slow kinetics of desorption, rather than to the hydrogenation of the non-basic species to basic ones. The experimental data for dibenzothiophene hydrodesulfurization in the presence of indole, indoline and o-ethylaniline was quantitatively represented by a modified Langmuir-Hinshelwood type rate equation.