The prediction of laminar flow in a bifurcating plane duct is presented. For a range of Reynolds numbers from 50 to 1500 and mass flow ratios in the junction from zero to the inflow massflux, the flow pattern and several global values, like pressure-drops, friction factors etc., are predicted. The aim of this investigation is to point out the relation between the energy losses and the parameters varied, which is possible by applying a parallel blockstructured multigrid code, with which, due to the high numerical efficiency of the algorithm and parallel computing, accurate results in short computing times are achievable, and therefore a high resolution of parameter fields are possible.