This study describes the results of a four-year research effort to develop inpatient and outpatient questionnaires that have sufficient validity and reliability to be used to measure patient perceptions of quality. As part of this effort, over 50,000 inpatients, emergency room patients, and ambulatory surgery patients from over 300 hospitals representing every US census region were surveyed. Separate questionnaires, called Quality of Care Monitors, were developed for inpatients and outpatients. The inpatient questionnaire consisted of 8 scales: Physician Care, Nursing Care, Medical Outcome, Courtesy, Food Service, Comfort and Cleanliness, Admissions/Billing, and Religious Care. The outpatient questionnaire had 7 scales: Physician Care, Nursing Care, Medical Outcome, Facility Characteristics, Waiting Time, Testing Services and Registration Process. The study found strong evidence of construct validity, predictive validity, and internal consistency for both questionnaires. Each questionnaire is capable of measuring separate dimensions of patient experience. A data bank developed from these questionnaires is currently accessed regularly by participating hospitals to assess quality improvement and to make benchmark comparisons with similar hospitals.