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Background and purpose: In amyotrophic lateral sclerosis (ALS), there is an unmet need for more precise patient characterization through quantitative, ideally operator‐independent, assessments of disease extent and severity. Radially sampled averaged magnetization inversion recovery acquisitions (rAMIRA) magnetic resonance imaging enables gray matter (GM) and white matter (WM) area quantitation in the cervical and thoracic spinal cord (SC) with optimized contrast. We aimed to investigate rAMIRA‐derived SC GM and SC WM areas and their association with clinical phenotype and disability in ALS. Methods: A total of 36 patients with ALS (mean [SD] age 61.7 [12.6] years, 14 women) and 36 healthy, age‐ and sex‐matched controls (HCs; mean [SD] age 63.1 [12.1] years, 14 women) underwent two‐dimensional axial rAMIRA imaging at the inter‐vertebral disc levels C2/3–C5/C6 and the lumbar enlargement level Tmax. ALS Functional Rating Scale–revised (ALSFRS‐R) score, muscle strength, and sniff nasal inspiratory pressure (SNIP) were assessed. Results: Compared to HCs, GM and WM areas were reduced in patients at all cervical levels (p < 0.0001). GM area (p = 0.0001), but not WM area, was reduced at Tmax. Patients with King's Stage 3 showed significant GM atrophy at all levels, while patients with King's Stage 1 showed significant GM atrophy selectively at Tmax. SC GM area was significantly associated with muscle force at corresponding myotomes. GM area at C3/C4 was associated with ALSFRS‐R (p < 0.001) and SNIP (p = 0.0016). Conclusion: Patients with ALS assessed by rAMIRA imaging show significant cervical and thoracic SC GM and SC WM atrophy. SC GM area correlates with muscle strength and clinical disability. GM area reduction at Tmax may be an early disease sign. Longitudinal studies are warranted. [ABSTRACT FROM AUTHOR]