Distinct X-ray intensity peaks corresponding to a stacking fault structure have been observed in the plastically deformed ctbrass (30% Zn). TITO sets of intensity peaks were present simultaneously: one set corresponding to the f.c.c. structure of annealed a-brass, the second set was displaced with respect to the first set in accordance with the Paterson pattern for a stacking fault structure. With Increasing plastic deformation the height and width of the stacking fault peaks increased, while the height of f.c.c. peaks decreased. Finally, only the intensity peaks of the stacking fault structure were observed. The positions of the stacking fault peaks and the original structure peaks remained constant and were independent of the amount of plastic deformation.