One of the most frequently used health status measures consists of a single item that asks respondents to rate their overall health as excellent, good, fair, or poor. This study identified the conceptual domain that is assessed by this self-rated health measure. Findings from 158 in-depth interviews revealed that the same frame of reference is not used by all respondents in answering this question. Some study participants think about specific health problems when asked to rate their health, whereas others think in terms of either general physical functioning or health behaviors. The data further revealed that the specific referents that are used vary by age. In addition, more tentative findings suggest that the use of specific referents may also vary by education and race. Finally, the results suggest that certain referents may not be related to closed-ended health ratings in predictable ways.