Book excerpt: This book provides a description of cognitive impairment in the elderly population through the lens of Thai Traditional Medicine as it is practiced in northern Thailand. It provides an overview of Thai Traditional Medicine and the memory loss presented in elderly dementia. Some medicinal plants used by traditional Thai healers to treat cognitive decline and memory issues in the elderly are reviewed. Medicinal Plants of Northern Thailand for the Treatment of Cognitive Impairment in the Elderly provides readers with the detailed description of the in vitro screening of ten plants and those results. The bioactivity of these single plants exemplifies the success of using an ethnobotanical filter to identify plants with cognitive enhancing activity.