The patient, a 77-year-old man, was diagnosed with senile depression. He was also diagnosed with depression at other hospitals, and pharmacotherapy by antidepressants was carried out. He was given sulpiride, selective serotonin reuptake inhibitors, a serotonin-norepinephrine reuptake inhibitor, an atypical antidepressant, and tricyclic and tetracyclic antidepressants, but conventional pharmacotherapies using these antidepressant drugs did not alleviate his symptoms. The patient was then administered 0.5 mg/day of clonazepam at bed time. Following 2 weeks of administration, his symptoms were alleviated. The dosage of clonazepam was increased to 0.75 mg/day and remission was facilitated. Four weeks later, the patient displayed further alleviation of his depressive symptoms, so he has been continued on 0.75 mg/day of clonazepam. Essential drug selections for senile depression includes selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and atypical antidepressants, but when these are ineffective, tricyclic antidepressants or tetracyclic antidepressants are alternatively selected. When a patient’s symptoms are not alleviated by essential drug selection, as occurred in the current case, clonazepam is considered to be another therapeutic candidate. If they fail to alleviate symptoms, however, then early referral to a specialist is crucial. Enhancing primary-care physicians’ understanding of senile depression and coordination with specialists is essential in the medical care of elderly patients with depression.