Purpose: To develop and test the validity and reliability of the Life Sustaining Treatment Attitude Questionnaire (LSTAQ), a survey instrument to elicit family member decision-maker attitudes toward life sustaining treatments for the critically ill at end of life. Background: Attitudes toward life sustaining treatments (LST) have been shown to influence decision-making at end of life (EOL). A reliable and valid tool to elicit attitudes specifically from family member decision-makers may help healthcare professionals facilitate decision-making during serious illness at end of life. Methods: A 33-item LSTAQ instrument was tested in 170 adults. Construct validity was evaluated by exploratory factor analysis. Correlations established convergent and discriminant validity. Reliability testing for internal consistency was assessed by Cronbach's alpha and corrected split half reliability coefficients. All procedures were done with Statistical Package for Social Sciences (SPSS version 18) software (SPSS Inc., Chicago, 111). Results: A 30-item final LSTAQ tool was derived from this study. Principal components factor analysis extracted six factors explaining 62.7% of variance. Correlations with a similar tool supported convergence (r = .72, ? <.01). Discriminant validity was confirmed by the absence of significant correlation with the dissimilar tool. LSTAQ internal consistency was good (Cronbach's alpha = .92). A preliminary exploration of differences in LSTAQ scores by ethnicity revealed a sampling size and distribution that was not optimally responsive to detection of ethnic differences. Conclusion: The LSTAQ is a reliable and valid tool to elicit LST attitudes specifically from family member decision-makers. The knowledge gained may help healthcare professionals promote interventions that facilitate family decision-making on life support for the ill relative at end of life. This might help reduce decision difficulties that cause preventable discomfort, unnecessary treatment and prolonged suffering for the terminally ill patient, as well as avoidable distress among family members involved in decisions for the sick relative.