Seventeen elderly patients with treatment-resistant depression were reassessed 15 months and 4 years after treatment with an antidepressant agent or ECT. At 15 months 47% (seven of 15) were clinically improved, and at the 4-year follow-up 71% (10 of 14) were improved. These results indicate that treatment-resistant depression may improve over time because of either the natural course of the illness or persistent treatment efforts.