In this paper, the behavior of the internal nozzle flow of a standard diesel fuel has been compared against a biodiesel fuel (soybean oil) at cavitating and non-cavitating conditions, using a homogeneous equilibrium model. The model takes into account the compressibility of both phases (liquid and vapour) and use a barotropic equation of state which relates pressure and density to calculate the growth of cavitation. Furthermore, turbulence effects have been introduced using a RNG k- ¿ model.The comparison of both fuels in a real diesel injector nozzle has been performed in terms of mass flow, momentum flux, effective velocity at the outlet and cavitation appearance. The decrease of injection velocity and cavitation intensity for the biodiesel noticed by numerical simulation at different injection conditions, predict a worse air-fuel mixing process. ; Generalitat Valenciana [GV/2009/031] ; F.J. Salvador; Martínez López, J.; Romero Bauset, JV.; M.-D. Roselló (2011). Influence of biofuels on the internal flow in diesel injector nozzles. Mathematical and Computer Modelling. 54(7):1699-1705. doi:10.1016/j.mcm.2010.12.010. ; Senia ; 1699 ; 1705 ; 54 ; 7