A random sample of adults (18 years and older) was drawn from members who had made a health care visit within the last 365 days to 1 of the 48 physician groups. Each of these members was mailed a 12-page questionnaire (provided in both English and Spanish), a cover letter, $2 in cash, and a return envelope. One week later, each individual in the sample was mailed a reminder and thank-you postcard. Two weeks later, nonrespondents received a second packet of materials and a reminder telephone call was attempted (up to 6 calls per person). The questionnaire included 153 items that assessed the following: (1) intention to switch to another physician group; (2) intention to switch to another health plan; (3) ratings of care: overall quality of care, quality and convenience of care, access to care, office waiting time, choice of primary care provider, and coverage for mental health care; (4) reports about care: appointment waiting time, office waiting time, continuity of care, and health promotion and disease prevention services; (5) utilization: number of visits in last 4 weeks, time since last visit, and use of urgent care services; (6) health status10,11; (7) presence of chronic conditions: hypertension, myocardial infarction, congestive heart failure, diabetes, angina, cancer, migraines, cataracts, glaucoma, macular degeneration, chronic allergies or sinus trouble, seasonal allergies, arthritis, sciatica or chronic back problems, vision trouble, chronic lung disease, liver trouble, dermatitis or other chronic skin rash, stomach trouble, deafness or other trouble hearing, kidney problems, limitation in use of an arm or leg, blurred vision, epilepsy, and thyroid problems; and (8) background information: age, sex, race, education, marital status, income, type of health insurance, and time enrolled in health plan.