Order-disorder transition conditions for wurtzite InxGa1-xN are represented. Two types of ordered InxGa1-xN are considered. In the first type, alternating (11 (2) over bar0) planes of the cation sublattice are mainly occupied by In and Ga, respectively. The second type corresponds to the wurtzite-type structure of alpha-BeSiN2. The decrease of the strain energy is a cause of the formation of the superstructure in wurtzite InxGa1-xN. The order-disorder transition should be continuous. At 0 degrees C the range of ordered InxGa1-xN extends from x=0.14 to x=0.96. At higher temperatures the ordered states are also in the vast composition ranges. In0.575Ga0.425N possesses the maximal temperature of the phase transition equal to 1140 C. The significantly larger ordering in InN-rich alloys in comparison with GaN-rich is a result of the asymmetry of the strain energy. (C) 2012 Elsevier B.V. All rights reserved.