This paper discusses two different approaches to assessing quality of life in the context of cancer clinical trial participation. Drawing on empirical evidence from a study of patients' experiences of phase I and II anti-cancer drug trial participation, the paper demonstrates how different methods of collecting data about an individual's quality of life (questionnaires and interviews) can lead to alternative conclusions about patients' trial experience and the impact of trial involvement on their quality of life. Data obtained from the quality of life questionnaires interestingly revealed no statistically significant differences in any of the scores over time while in-depth interviews uncovered something of the psychological, emotional and social impact of taking part in a clinical trial from the perspective of the patient. The paper concludes by reflecting on some of the methodological issues that arise when assessing the quality of life of patients with a life threatening disease in clinical trials.