A structural interview covering the DSM-III criteria for major depression was adapted for separate use with Alzheimer's disease patients and with their families. Data from 36 patients yielded a depression rate of 13.9%, whereas information from their families indicated that the rate was 50.0%. This disagreement reflected greater family endorsement of patients' loss of interest or pleasure, irritability, fatigue, and feelings of worthlessness. Use of DSM-III-R criteria narrowed but did not eliminate the discrepancy between patients' and families' assessments of the patients' depression. Uniform procedures for gathering and integrating data from the family that are relevant to diagnosis in this group are indicated.