Over the last decade, changes in health care delivery and concern with costs and with dramatic variations in practice between regions, institutions and even physicians at the same institution have led the administrators and health politicians to focus on the outcomes of medical care. The Agency for Health Care Policy and Research was established with the objective of fostering research on the outcomes of medical interventions and on the development of guidelines. The Agency supports studies based not only on standard outcomes such as mortality and morbidity, but also on quality of life and patient satisfaction. The Patient Outcome Research Teams (PORTs) projects are the showcase displays of the Agency, and their goals are to identify and analyze the outcomes and costs of alternative interventions for a given clinical condition, in order to determine the most effective and cost-effective means to prevent, diagnose, treat, or manage it and develop and test methods for reducing inappropriate or unnecessary variations. Three PORTs are focused on the following cardiovascular conditions: acute myocardial infarction, chronic ischemic heart disease and stroke. There are many situations in which randomized clinical trials are not feasible and large-scale observational studies are necessary to generate information about what happens in the real practice. This information deepens the understanding of practical effectiveness as opposed to theoretical efficacy since trials do not always measure all the outcomes of interest to patients and physicians. One way to solve the problem of inaccurate data of observational studies is by establishing a specific registry to measure in an efficient way key patient characteristics, process of care elements and relevant outcomes. The Cardiac Surgery Reporting System is a registry that collects clinical data on all patients undergoing cardiac surgery in New York State. This registry has produced reliable and valid measures of quality and hospitals and cardiac surgery programs throughout New York use this information to improve outcomes for their patients. Health related quality of life can be a useful outcome measure in the assessment of clinical effectiveness. However, there are still many methodological questions regarding the validity and sensitivity of quality of life measurement an optimal study design calls for caution in the interpretation of current results and makes refinement of methodological issues a desirable goal. Nevertheless, apparently valid studies of cardiovascular diseases and interventions using health related quality of life as an outcome measures have been reported where such measures have provided information about undesirable side effects of medications and the impact of the intervention on the health related quality of life. Moreover, some of these studies have identified different patterns of health care as leading to different quality of life outcomes. Thus, quality of life measurement appears as a technology which holds promise for the future assessment of clinical effectiveness.