The planar channel entry flow of a Newtown fluid containing neutrally buoyant, non-Brownian, slender particles is studied numerically. In particular, the effects of Reynolds number, Re, and a nondimensional suspension parameter, C, on the developing velocity and orientation fields are investigated. The governing orientation equations are solved along particle paths, whereas the flow kinematics is determined from an Eulerian viewpoint. The fourth-order orientation tenser, which characterizes the orientation structure, is obtained from the differential orientation evolution equations and also from the Lagrangian description of the orientation angles of a number of fictitious fibers in the orientation space. It is found that both the second- and fourth-order orientation evolution equations, if used with quadratic closure approximations, inaccurately predict an earlier alignment of fibers in the flow direction. Furthermore, for higher values of suspension parameter C, convergent results are not obtained by using such evolution equations. On the other hand, the results obtained by following a number of orientation angles indicate that the entry length increases linearly with C, and the effect of Reynolds number on the entry length becomes negligible for high C values.