We described here five patients with Alzheimer's disease (AD) who have behavioral and psychological symptoms of dementia (BPSD), and who have shown a remarkable improvement as a result of Yokukansan treatment. All five patients exhibited irritability and excitement, four of the patients suffered from aggression and insomnia, and three suffered from wanderings. All of the patients started recovering from these symptoms within 1-2 weeks from the start of the treatment, without any adverse reaction. In conclusion, our case study suggests that Yokukansan is a safe and effective treatment for AD patients with BPSD. Our study further suggests that Yokukansan is especially useful for patients who are difficult to treat with neuroleptics, such as patients with insomnia and wandering, patients exhibiting a depressive state as well as irritability and excitement, and those with physical symptoms, including gait disturbances and urinary incontinence.