Abstract:In this article we study the product action of the direct product of automorphism groups of graphs. We generalize the results of Watkins [J. Combin Theory 11 (1971), 95--104], Nowitz and Watkins [Monatsh. Math. 76 (1972), 168--171] and W. Imrich [Israel J. Math. 11 (1972), 258--264], and we show that except for an infinite family of groups S n ×S n , n ≥ 2 and three other groups D 4 ×S 2 , D 4 ×D 4 and S 4 ×S 2 ×S 2 , the direct product of automorphism groups of two graphs is itself the automorphism group of a graph.