A method for the interpretation of Warren-Averbach mean-squared strain curves is presented. If a polynomial is fitted to such a mean-squared strain curve, then the coefficients of this polynomial can be expressed simply in the mean-squared local strain in the direction perpendicular to the diffracting planes and the mean-squared derivatives of this strain. The method is applied to a series of X-ray diffraction line broadening measurements of isochronally recovery-annealed aluminium. The changes in the average squared derivatives observed after different anneals are explained as changes in the dislocation arrangements in the specimen. The parameters obtained by the method are found to be sensitive to small changes in the strain fields.