This paper discusses the state of the science in prospective measurement in end-of-life research and identifies particular areas for focused attention. Topics include defining the scope of inquiry, evaluating experiences of patients too ill to communicate, the role of proxy and family response, measurement sensitivity to change, the role of theory in guiding measurement efforts, evaluating relationships between domains of end-of-life experience, and measurement of cultural comprehensiveness. The state of the sciences calls for future research to (1) conduct longitudinal studies to capture transitions in end-of-life trajectories; (2) evaluate the quality of proxy reporting as it varies by rater relationship, domain, and over time; (3) use state-of-the art psychometric and longitudinal techniques to validate measures and to assess sensitivity to change; (4) develop further and test conceptual models of the experience of dying; (5) study the inter-relatedness of multiple dimensions of end-of-life trajectories; (6) compile updated information evaluating available measurement tools; and (7) conduct population- based research with attention to ethnic and age diversity.