A 31-year-old Taiwanese man with a history of schizophrenia had received risperidone and quetiapine during past outpatient records without adverse extrapyramidal reactions. Recently, he had received quetiapine 400 mg daily for 2 weeks, which was discontinued because of excessive somnolence; he was then switched to aripiprazole 15 mg daily. Within 1 month after initiating aripiprazole, he was found lying on the floor with fluctuating consciousness and muscle weakness. The patient was afebrile (36°c), with blood pressure of 113/68 mmHg, pulse of 120 bpm, and respiratory rate of 18 rpm. Neurological examination revealed intermittent disorientation, slurred and incoherent speech, fluctuating consciousness, and weakness of bilateral lower extremities. Laboratory findings included an elevated CK, peaking at 19,660 IU, and an elevated serum glutamate oxaloacetate transaminase, peaking at 238 IU/liter. His WBC count was 16,620mm3, and a routine urine specimen showed presence of myoglobin. His toxicology screen was negative. NMS was not considered because of the lack of autonomic instability and fever. During the hospitalization, supportive therapies were instituted, with close monitoring and treatment. He was treated with high-volume intravenous solution replacement daily, which improved his consciousness. After 3 days, the serum CK level fell to 6,348 IU and continued to normalize through regular follow-up after discharge.