Nurse researchers are increasingly combining qualitative and quantitative methods in order to understand more fully the world of research subjects. Qualitative data are often used to explore the subjective meanings behind survey responses and to develop quantitative measures and scales. Insights from qualitative data help researchers to design instruments which are more sensitive to respondents' meanings and interpretations. The aim of this paper is to highlight the epistemological and methodological complexities involved in this enterprise through drawing on our own experience of developing an instrument to examine person-centredness in health care from a qualitative study of dissatisfaction. The intricacies of this project relate to: epistemological continuity and inconsistency; research roles; reflexivity; confirmation; and completeness. Through discussing the literature around integrating methods, we suggest that researchers could be assisted in their attempts to develop conceptually sound quantitative measures by extending the concept of reflexivity (used in qualitative research) to the quantitative components of mixed method studies. This would aid conceptual clarity by making explicit the social, cultural, and political construction of knowledge, and would also encourage researchers to reflect upon the ethical and political consequences of their research.