Although evidence of effectiveness is limited, care management based outside primary care practices or hospitals is receiving increased attention. The University of Michigan (UM) Complex Care Management Program (CCMP) provides care management for uninsured and underinsured, high-utilizing patients in multiple primary care practices. To inform development of optimal care management models, we describe the CCMP model and characteristics and health care utilization patterns of its patients. Of a consecutive series of 49 patients enrolled at CCMP in 2011, the mean (SD) age was 48 (+/- 14); 23 (47%) were women; and 29 (59%) were White. Twenty-eight (57%) had two or more chronic medical conditions, 39 (80%) had one or more psychiatric condition, 28 (57%) had a substance abuse disorder, and 11 (22%) were homeless. Through phone, e-mail, and face-to-face contact with patients and primary care providers (PCPs), care managers coordinated health and social services and facilitated access to medical and mental health care. Patients had a mean (SD) number of hospitalizations and emergency room (ER) visits in 6 months prior to enrollment of2.2 (2.5) and 4.2 (4.3), respectively, with a nonstatistically significant decrease in hospitalizations, hospital days, and emergency room visits in 6 months following enrollment in CCMP. Centralized care management support for primary care practices engages high-utilizing patients with complex medical and behavioral conditions in care management that would be difficult to provide through individual practices and may decrease health care utilization by these patients.