Abstract. Let G be the circulant graph C n (S) with S ⊆ {1, 2, . . . , ⌊ n 2 ⌋}, and let I(G) denote its the edge ideal in the ring R = k[x 1 , . . . , x n ]. We consider the problem of determining when G is Cohen-Macaulay, i.e, R/I(G) is a Cohen-Macaulay ring. Because a Cohen-Macaulay graph G must be well-covered, we focus on known families of wellcovered circulant graphs of the form C n (1, 2, . . . , d). We also characterize which cubic circulant graphs are Cohen-Macaulay. We end with the observation that even though the well-covered property is preserved under lexicographical products of graphs, this is not true of the Cohen-Macaulay property.

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