Abstract.A B h set (or Sidon set of order h) in an Abelian group G is any subset {b0, b1, . . . , bn} of G with the property that all the sums bi 1 + · · · + bi h are different up to the order of the summands. Let φ(h, n) denote the order of the smallest Abelian group containing a B h set of cardinality n + 1. It is shown thatwhere δl(△ n ) is the lattice packing density of an n-simplex in Euclidean space. This determines the asymptotics exactly in cases where this density is known (n ≤ 3) and gives improved bounds on φ(h, n) in the remaining cases. The corresponding geometric characterization of bases of order h in finite Abelian groups in terms of lattice coverings by simplices is also given.