Increased interest in the patient-centered medical home (PCMH) among policy makers and practitioners has resulted in a growth of research on the factors that influence its adoption and implementation, yet this research often fails to capture the multidimensional nature of the PCMH and the longitudinal nature of the implementation process. This study documented physician practices’ PCMH capacity across 12 different domains (e.g., extended access, specialist referral, use of patient registry) over a 3-year period (2008-2010). Linear growth models indicated that participation through different types of physician organizations and practice size were associated with different baseline levels of capacity and changes in capacity over time; however, the association varied as a function of the different PCMH dimensions. Differences in PCMH capacity across the 12 domains and time suggest that more attention should be paid to the longitudinal nature of PCMH implementation and the differential challenges associated with its component parts.