Around the world, adults with serious illnesses or chronic conditions account for a disproportionate share of national health care spending. We surveyed patients with complex care needs in eleven countries (Australia, Canada, France, Germany, the Netherlands, New Zealand, Norway, Sweden, Switzerland, the United Kingdom, and the United States) and found that in all of them, care is often poorly coordinated. However, adults seen at primary practices with attributes of a patient-centered medical home--where clinicians are accessible, know patients' medical history, and help coordinate care--gave higher ratings to the care they received and were less likely to experience coordination gaps or report medical errors. Throughout the survey, patients in Switzerland and the United Kingdom reported significantly more positive experiences than did patients in the other countries surveyed. Reported improvements in the United Kingdom tracked with recent reforms there in health care delivery. Patients in the United States reported difficulty paying medical bills and forgoing care because of costs. Our study indicates a need for improvement in all countries through redesigning primary care, developing care teams accountable across sites of care, and managing transitions and medications well. The United States in particular has opportunities to learn from diverse payment innovations and care redesign efforts under way in the other study countries.