The Rietveld profile‐analysis refinement procedure [Rietveld,J. Appl. Cryst.(1969),2, 65–71] is here applied to microdensitometer‐measured Guinier–Hägg X‐ray powder film data (strictly monochromated CuKα1radiation). Various functions for describing the profile form of an individual reflection are tested; the most satisfactory fit is obtained for a modified and asymmetrized Lorentz function. The crystal structure of α‐Bi2O3has been refined and no significant deviations are observed from the results of an earlier single‐crystal study [Malmros,Acta Chem. Scand. (1970),24, 384–396]. AnRFvalue [roughly comparable with the conventionalR(F) value of single‐crystal work] of 0.068 was obtained, with standard deviations on the refined positional parameters on average three times larger than those obtained from the single‐crystal study. Further examples of the refinement technique are also given which illustrate both its reproducibility an