For which commutative Noetherian rings A is Spec(A), the set of prime ideals of A, order-isomorphic under inclusion to Spec(Z[x]), the prime ideals of the polynomial ring in one variable over the integers? We show that this is true for every finitely generated birational extension of the polynomial ring in one variable over an order D in an algebraic number field; that is, if B is an intermediate ring between D[x] and its quotient field and B is finitely generated over D[x], then Spec(B) congruent to Spec(Z[x]). (c) 2005 Elsevier B.V. All rights reserved.