The defocusing of the diffracted beam in a texture goniometer using the reflexion technique for the determination of the preferred orientation is discussed. By means of textureless (random) specimens of the ferromagnetic material Ba3CozFez.,O4~ this defocusing is measured for several diffraction planes in two cases: (1) a narrow and (2) a wide receiving slit. Calibration functions to correct for defocusing effects are calculated using an equation given by Gale & Griffiths [ Brit. J. Appl. Phys. (1960). 11, 96-102]. The calculated functions plotted rersus the angle of specimen tilt are compared with the relative intensities measured on random specimens.