Rivastigmine, galantamine, and memantine, in addition to donepezil, which has been on the market over 10 years, have been available for the treatment of Alzheimer's disease (AD) since 2011 in Japan, leading a new stage in the medical treatment of AD. We studied two AD patients showing sudden deterioration of behavioral and psychological symptoms of dementia (BPSD) associated with switching from rivastigmine to donepezil after the clinical trial of rivastigmine. In the patients, rivastigmine seemed to be more beneficial than donepezil for the control of BPSD. Although It was not obvious whether their different responses to the two cholinesterase inhibitors were due to the different pharmacological profiles, ie, the presence of inhibition of butyrylcholinesterase in rivastigmine, a particular cholinesterase inhibitor might be more effective in particular AD cases. Further investigations are needed to confirm the difference, and to identify the measures for selecting the most appropriate medication for each AD patient.