Development and validation of a questionnaire about the main variables affecting the individual investor's behavior in the Stock Exchange. There is a considerable lack of information about the methodology usually used in most of the studies about individual investor's behavior. The studies reviewed do not show the method used in the selection of the items or the psychometric properties of the questionnaires. Because of the importance of investment in the Stock Exchange nowadays, it seems relevant to obtain a reliable instrument to understand individual investor's behavior in the Stock Exchange. Therefore, the goal of the present work is to validate a questionnaire about the main variables involved in individual investors' behavior in the Stock Exchange. Based on previous studies, we elaborated a questionnaire using the Delphi methodology with a group of experts. The internal consistency (Cronbach alpha=.934) and validity evidence of the questionnaire show that it may be an effective instrument and can be applied with some assurance.