Two Boundary Element Method (BEM) approaches are implemented in the simulation of the filling of isotropic fiber-reinforced preforms used in Resin Transfer Molding (RTM). One is a pure BEM approach used in homogeneous domains where the permeability remains constant in the space; the other one is a Dual reciprocity boundary element method (DR-BEM) approach employed in non-homogeneous domains where the permeability changes as a known function. Five cases are briefly discussed: the first two cases deal with a homogeneous domain and piecewise constant pressure and constant flow regimes; the third case considers gravitational effects in a constant pressure injection conducted in a homogeneous domain; the last two cases deal with constant pressure and constant flow injections in a non-homogeneous domain where the permeability changes in radial form. The accuracy of the BEM approaches is evaluated by comparing the numerical results obtained in the simulations with analytical, experimental and numerical results of other authors. In addition to the accuracy assessment of the approaches implemented, in the present research, both flow regimes for the same homogeneous domain are compared and the influence of the change of the fiber volume fraction presented in the non-homogeneous domain is analyzed on the behavior of the radial pressure profile.