The growth of delta' particles in an Al-2Li-5Mg-0.1Zr (wt.%) alloy was studied by means of electrical resistivity and small angle X-ray scattering measurements. The particle development in the ageing temperature interval studied obeys the growth law. Criteria of the coarsening process of the delta' phase were examined. The activation energy for the coarsening process was determined to be 1.34 +/- 0.02 eV. (C) 2002 Elsevier Science B.V. All rights reserved.