Dropout, or disengagement, from medical homes is being increasingly linked with poor health outcomes in children. Although most of the studies of this problem have been based on incomplete assessments and cross-sectional designs, there is evidence that most children who fail to return to their medical home do not obtain care from another source. A recent study revealed that 34 percent of children disengaged from pediatric preventive care by 12 months of age and that 50 percent disengaged by 24 months of age. In addition, the assessment of vaccination coverage rates was significantly and adversely affected by disengagement. Among the confluence of factors resulting in disengagement, the most important is the amount of time and resources that parents can devote to the appropriate use of medical homes. There is an urgent need for strategies designed to reengage children “lost” from medical homes.