his paper presents a study of the influence of plastic and non-plastic fines on the resistance of sands to liquefaction. The study is carried out with the aid of a triaxial apparatus on reconstituted sand-fines mixtures at low fines content (≤ 5%). A description of the soils used in this study is first presented followed by the presentation of results of undrained monotonic liquefaction tests performed on sand specimens containing different fines fractions. Experimental results show that the increase in non-plastic fines content up to 5% increases the resistance of sand to liquefaction. Whereas the increase in plastic fines content reveals a decrease in the latter. This result is due to the contribution of the non-plastic fine particles to the overall chain forces and therefore they increase the resistance against liquefaction, however the decrease in the resistance with plastic fines could be attributed to their nature that lead to the sliding between the sand grains and therefore favour the contractancy of the whole specimen.