“Mr. A,” a 52-year-old man with a diagnosis of bipolar I disorder, had been hospitalized for mania with psychosis at age 34 and had shown partial response to various antipsychotics and mood-stabilizers. At age 38 he took clozapine, 600 mg/day, and experienced full symptom remission and a return to good psychosocial functioning. He developed disabling checking behaviors 2 years later, which were relieved with sertraline, 200 mg/day. At age 50, the patient insisted on discontinuing clozapine and sertraline. At 100 mg/day of clozapine, his obsessive-compulsive symptoms completely resolved. However, within 2 months, the patient developed a full manic episode requiring hospitalization. He was stabilized on clozapine, 300 mg/day, and discharged, but within 4 months, the checking behaviors returned and sertraline was restarted, bringing partial relief. A year later, he again insisted on reducing the clozapine dosage, and the cycle of obsessive-compulsive symptom remission, mania, response to clozapine, re-emergence of obsessive-compulsive symptoms, and improvement with sertraline was observed.