In order to understand the formation of jets from young stars, the amount of collimation caused by the interaction of an outflow from a proto-star with the aspherical accreting environment was studied. Both the low and high cooling regimes were analysed and it was found that in both cases perfectly collimated beams can be formed. Time and length scale considerations indicate that the interaction cannot be solely responsible for the collimation and that other process such as magnetic collimation are important as well. This work does show that the influence of the environment can be substantial for the collimation of proto-stellar jets.