Quality may appear to be a nebulous term. The U.S. Office of Technology Assessment has defined the quality of medical care as "evaluation of the performance of medical providers according to the degree to which the process of care increases the probability of outcomes desired by patients and reduces the probability of undesired outcomes, given the state of medical knowledge." The Institute of Medicine (IOM), in a report entitled, "Medicare: A Strategy for Quality Assurance,"stated that "quality of care is the degree to which health services for individuals and populations increase the likelihood of desired health outcomes and are consistent with current professional knowledge," whereas Ovretveit (1992) simply states, "A quality health service/system gives patients what they want and need." All of these definitions may provide the best explanation of the concept of quality in health care. Each provides additional insight into quality, what we can expect from quality, and how quality can be perceived. Pharmacy service quality has been measured by assessing its structure, process, and outcomes.