Objective: To develop and validate a subjective measure of cognitive fatigue the State-Trait Inventory of Cognitive Fatigue in community dwelling older adults. Design: Scale development and test construction. Setting: Community-dwelling older adults enrolled in a longitudinal cohort aging study. Participants: Participants (N=175) were healthy, English-speaking, community-dwelling adults, age >= 65 years. Interventions: Not applicable. Main Outcome Measures: State-Trait Inventory of Cognitive Fatigue total, cognitive fatigue, motivation, mental effort, and boredom summation scores for both state and trait forms. Results: Principal component analysis yielded the expected 4 components for both state and trait forms: cognitive fatigue, mental effort, motivation, and boredom. All components had good reliability. There was good convergent validity as measured by the strong positive relation between cognitive fatigue and a subjective measure of general fatigue, even after controlling for depressive symptoms. Greater subjective cognitive fatigue was associated with worse performance on measures thought to be more sensitive to aspects of executive functioning. Conclusions: This study developed and established the psychometric properties of a new instrument for the subjective measurement of cognitive fatigue for use in community-dwelling older adults. The State-Trait Inventory of Cognitive Fatigue's relatively brief administration time (<10min; mean, 5.6 +/- 2.9) and strong psychometric properties support its utility in both research and clinical settings. Future studies should establish the psychometric properties of this scale in other populations and examine its predictive utility for relevant clinical outcomes. (C) 2016 by the American Congress of Rehabilitation Medicine