To determine whether delirium can be diagnosed by telephone, we interviewed 41 subjects aged 65 years or older 1 month after repair of hip fracture, first by telephone and then face-to-face. Interviews included the modified telephone Mini-Mental State Examination and the Delirium Symptom Interview. Delirium was diagnosed using the Confusion Assessment Method diagnostic algorithm, and the telephone results were compared with the face-to-face results (the "gold standard"). Of 41 subjects, 6 were delirious by face-to-face assessment; all 6 were delirious by telephone (sensitivity 1.00). Of 35 patients not delirious by face-to-face assessment, 33 patients were not delirious by telephone (specificity = 0.94). We conclude that telephone interviews can effectively rule out delirium, but the positive diagnosis should be confirmed by a face-to-face assessment, especially in populations with a low prevalence of delirium.