Approval of radiation countermeasures through the FDA Animal Rule requires pivotal efficacy screening in one or more species that are expected to react with a response similar to humans (21 CFR § 314.610, drugs; § 601.91, biologics). Animal models used in screening studies should reflect the dose response relationship (DRR), clinical presentation, and pathogenesis of lung injury in humans. Over the past 5 y, the authors have characterized systematically the temporal onset, dose-response relationship (DRR), and pathologic outcomes associated with acute, high dose radiation exposure in three diverse mouse strains. In these studies, C57L/J, CBA/J, and C57BL/6J mice received wide field irradiation to the whole thorax with shielding of the head, abdomen, and forelimbs. Doses were delivered at a rate of 69 cGy min− 1 using an x-ray source operated at 320 kVp with half-value layer (HVL) of 1 mm Cu. For all strains, radiation dose was associated significantly with 180 d mortality (p< 0.0001). The lethal dose for 50% of animals within the first 180 d (LD50/180) was 11.35 Gy (95% CI 11.1–11.6 Gy) for C57L/J mice, 14.17 Gy (95% CI 13.9–14.5 Gy) for CBA/J mice, and 14.10 Gy (95% CI 12.2–16.4 Gy) for C57BL/6J mice. The LD50/180 in the C57L/J strain was most closely analogous to the DRR for clinical incidence of pneumonitis in non-human primates (10.28 Gy; 95% CI 9.9–10.7 Gy) and humans (10.60 Gy; 95% CI 9.9–12.1 Gy). Furthermore, in the C57L/J strain, there was no gender-specific difference in DRR (p= 0.5578). The reliability of the murine models is demonstrated by the reproducibility of the dose-response and consistency of disease presentation across studies.