Let be Tnk the number of labeled graphs on vertices and treewidth at most (equivalently, the number o1 and some explicit absolute constant c>0. Disregarding terms depending only on k, the gap between the lower and upper bound is of order (log k)n. The upper bound is a direct consequence of the well-known formula for the number of labeled lambda-trees, while the lower bound is obtained from an explicit construction. It follows from this construction that both bounds also apply to graphs of pathwidth and proper-pathwidth at most k .