Reminiscing, the mental activity of dwelling on the past, was quantified during a semistructured interview known for its reliability. Eighteen depressed, hospitalized patients (mean age 62 years; DSM‐III major depressive disorder) were compared to 12 normals with equivalent demographic characteristics. The depressed patients prior to treatment had significantly lower reminiscing scores. When the interviews were repeated after 3–4 weeks, the 10 patients treated with ECT were significantly improved clinically and their reminiscing score had increased to normal levels. The eight patients who received antidepressant medication were non‐responsive to treatment and reminiscing was further reduced during their second interview. The role of reminiscing and its therapeutic potential in ageing are discussed.