Recently, selective serotonin reuptake inhibitors (SSRI) have been frequently used as the first choice of antidepressants because of their safety in comparison with tricyclic antidepressive agents (TCA). On the other hand, when SSRIs are not effective, they are frequently replaced with another antidepressant. In that case, a small dose of a TCA is often added without cross tapering. We report two elderly patients with depression who exhibited markedly low blood pressure when a small dose of a TCA was added to a SSRI. The combination of a SSRI and a TCA can be hazardous because it can cause unexpected adverse effects especially in elderly patients.