In a paper on F-rationality [J. Algebra 176 (1995) ] Donna Glassbrenner showed that over a field of odd characteristic p the Hilbert ideals of the tautological representations of the symmetric group Σ n and alternating group A n coincide if n ≡ 0, 1 mod p. She asked if this was always the situation in the modular case. We answer this in the affirmative using Macaulay's theory of irreducible ideals in polynomial algebras: a somewhat forgotten bywater of commutative algebra. As a bonus, the method yields applications back to the original question of F-rationality studied in [J. Algebra 176 (1995) 824-860]. 2004 Elsevier Inc. All rights reserved.Let ρ : G → GL(n, F) be a representation of a finite group G over the field F. Denote by V = F n the representation space on which G acts via ρ and F[V ] the algebra of polynomial functions on V . If z 1 , . . . , z n ∈ V * is a basis for the space of linear forms V * we use the alternate notation F[z 1 , . . . , z n ] for F [V ]. Associated with ρ is the subalgebra F[V ] G of invariant polynomial functions and the Hilbert ideal h(ρ) ⊂ F[V ]; the latter is the ideal in F[V ] generated by all the homogeneous invariant forms of strictly positive degree. If ρ is clear from context we simply write h(G) for the Hilbert ideal.In her study [2] of F-rationality of invariant rings Donna Glassbrenner proved that the Hilbert ideals of the symmetric group Σ n on n letters and its alternating subgroup A n coincide for the standard representation of Σ n on V = F n by permutation of the coordinates