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The Illinois high (IHP), low (ILP), and corresponding reverse (IRHP, and IRLP) protein–strains of maize represent genetic extremes for differences in grain protein concentration. The objective of this study was to determine how divergent selection for grain protein affects N use in hybrid plants. Inbreds derived from the protein–strains were crossed as males to a common tester and the resultant hybrids evaluated at eight N rates in the field over 3 years. A more than two-fold difference in grain protein concentration was observed among the strain-hybrids with ILP averaging 65gkg⁻¹, IRHP 89gkg⁻¹, IRLP 111gkg⁻¹, and IHP 148gkg⁻¹ of grain protein. Except for IHP at the lowest N levels, the strain-hybrids were similar in their whole shoot biomass production both pre- and post-flowering. Conversely, the strain-hybrids differed markedly in their uptake and accumulation of plant N, and these differences were already …