This paper describes the development and psychometric properties of a new scale for assessing the psychologic impact of genetic susceptibility testing for Alzheimer disease (AD). The new instrument, The REVEAL Impact of Genetic Testing for Alzheimer's disease (IGT-AD) was designed to examine the unique nature of genetic information and the disease course of AD. The scale was tested as a part of a multicenter clinical trial designed to evaluate the impact of AD risk assessment and data were collected from 276 participants in the study. Using an iterative process of principal component analysis and Cronbach [alpha], the final 16-item IGT-AD was found to have a 2-factor structure with excellent internal reliability. Construct validity was established by patterns of correlation with other standardized self-reported measures. This scale should be useful in the identification of patients who maybe susceptible to the negative effects of receiving genetic information, monitoring of patients who have received genetic information, and as a tool for researchers who wish to study the effects of genetic susceptibility testing for AD.