A 79-year-old male with mild probable AD and a history of late-onset anxiety and depression was evaluated for uncontrollable anger outbursts and agitation. He had become extremely argumentative with both his wife and his co-workers at a part-time job. When unable to complete a task he would become uncontrollably angry and grabbed his wife's wrists once. At the time of evaluation, the patient was taking donepezil 10 mg, bupropion 300 mg, lorazepam 0.5 mg, and trazodone 50 mg daily. He was started on lithium 150 mg, which was increased to 300 mg daily after two weeks. After 12 weeks of lithium treatment, he exhibited a significant decrease in angry thoughts, frustration, and irritability. His last recorded serum lithium level, after 8 weeks of treatment, was 0.32 mmol/L. He remained on lithium and continued to work part-time without any adverse events. He continued to decline cognitively with persistent but less severe agitation.