Theinsitunondestructive determination of the concentration profile in a small epitaxial binary diffusion couple by x‐ray‐diffraction line‐profile analysis is considered. On the basis of the work by Houska and collaborators, a direct method is presented for the determination of the concentration profile from an x‐ray intensity band. The method has the advantages that only a single order of the reflection is required and that neither iterative nor trial and error calculations are necessary as compared to previous methods. It is further shown that linear interpolation between both extremeties of the intensity band is a poor approximation to the actual background profile. The background mainly consists of thermal diffuse scattering (TDS) which peaks at the Bragg positions and may contribute significantly to the integrated intensities measured. An iterative method is proposed to calculate the TDS background. Both the direct method for determining the concentration profile and the calculation and subsequent elimination of the TDS background are applied to experiments with Cu/Ni bicrystals where the copper is either electrocrystallized or deposited from the vapor phase onto the 111 nickel substrate.