The early success of the demonstration Program of All-Inclusive Care for the Elderly (PACE) led to its designation as a permanent Medicare program in 1997. But the growth in the number of programs and enrollment has lagged and does not meet expectations. This article offers insights into the mechanisms influencing the expansion of PACE, from information obtained in interviews and surveys of administrators, medical directors, and financial officers in 27 PACE programs. Sixteen barriers to expansion were found, including competition, PACE model characteristics, poor understanding of the program among referral sources, and a lack of financing for expansion. This experience offers important lessons for providing integrated health care to the frail elderly.