a1 Polytechnic of Wales, Pontypridd, Wales
In  the question of the existence of perfect e-codes in the infinite family of distance-transitive graphs Ok was considered. It was pointed out that it is difficult to rule out completely any particular value of  because of the difficulty of working with the sphere packing condition. For e = 1, 2, 3 it can be seen from the results of  that the condition given by the generalisation of Lloyd's theorem is satisfied for infinitely many values of k. We shall show that this is not the case for e = 4 and we shall prove that there are no perfect 4-codes in Ok.
(Received April 26 1979)