The structure of Co2Al5 (hP28, P6(3)/mmc) was refined by means of Rietveld method. The shortest Co-Al distance amounts 2.338 Angstrom. Co2Al5 shows a homogeneity range between Co29Al71 and Co27.5Al72.5 at 1125 K. The concentration dependence of lattice parameters was also measured. The axial ratio c/a increases with increasing mole fraction of aluminum. (C) 1998 International Centre for Diffraction Data. [S0885-7156(98)00701-5]