A new technique for the unambiguous determination of dislocation line directions in macroscopic single crystals is presented. The technique is based on analysis of the projected directions of the images of the dislocations on synchrotron white beam topographs. Calculation is carried out in a pseudo-cubic axis system which is related to the crystal axis system by a transformation matrix. Final line directions are presented referred to the crystal axes. An example of the application of this technique to the analysis of growth dislocations in pyrene single crystals is presented.