The debate about adequate research methods for obtaining relevant results in clinical medicine and health care does not take place in a vacuum. In the present paper the longstanding debate about the epistemological underpinnings and methodological perspectives of qualitative and quantitative research methods in the social sciences is outlined and fructified for evidence-based medicine and health care. By using examples from research practice we will demonstrate that both the utilisation of qualitative methods and the use of a "mixed methods" design may contribute to the current methodological debate and improve research practice in evidence-based health care.