For a vertex v of a connected oriented graph D and an ordered set W = [wi, w2,.. •, wk} of vertices of D, Ihe (directed distcince) representation of v with respect to W is the ordered fc-tuple r(v \ W) = (d(v, w1),d(v, w2 ), •.. ,d(v, wk )), where d(v, wi ) is Ihe directed distance from v to wi . The set W is a resolving set for D if every two distinct vertices of D have distinct representations. The minimum cardinality of a resolving set for D is the (directed distance) dimension dhn(D) of D. The dimension of a connected oriented graph need not be defined. Those oriented graphs with dimension 1 are characterized. We discuss the problem of determining the largest dimension of an oriented graph with a fixed order. It is shown that if the outdegree of every vertex of a connected oriented graph D of order n is at least 2 and dim(D) is defined, then dim(D) ≤ n - 3 and this bound is sharp.