Given the recognized need to examine cost-effectiveness data in addition to clinical data when making decisions relating to choice of clinical interventions, there is a growing interest and experience in undertaking economic evaluations alongside clinical trials. It has been argued, when an economic evaluation is necessary for assessing the cost-effectiveness of a medical intervention, the integration of both the medical and clinical issues need to be included at the start of designing a clinical trial. A proposal has been made for how clinical researchers and health economists may cooperate successfully at the successive phases in designing a clinical trial. Therefore, discussion points for clinical researchers and health economists are given, and the possible methodological consequences of adding an economic evaluation to a trial are addressed.