In crystal structure determination with presence of heavy atoms, Patterson method and methods based on it, i.e. the heary atom method, the isomorphous replacement method and the anomalous scattering method are conventionally employed. When applying these methods ambiguities in results often arise. It had been suggested by one of the present authors in 1965 that the ambiguities can be eliminated by using the direct method. In recent years, similar investigations are continued abroad. These methods not only present their distinctive feathures in the work of structure analysis of crystals of small molecules, but their further developements will be effec-tive in extension the field of application of direct methods in structure analysis of biological macro-molecular crystals, making contribution on improving the state of art of these studies. The application of the method in the case of centric symmetry have been demonstrated in the published work of one of the present authors. Another successful example on the case of non-centric symmetry is given here. Although only the problem of ambiguity of Patterson method is treated in this example, but the same approach can be applied to that of the isomorphous replacement method and the anomalous scattering method.