Our analyses of federal survey data show that more than four in five office-based physicians could qualify for new federal incentive payments to encourage the adoption and "meaningful use" of electronic health records, based on the numbers of Medicare or Medicaid patients they see. The incentives are thus likely to accelerate the spread of electronic health records. However, our analyses also indicate that eligibility for the incentives is likely to vary by specialty: 90.6 percent of physicians working in general or family practice or internal medicine could qualify for incentives, but fewer than two-thirds of pediatricians, obstetrician-gynecologists, and psychiatrists may qualify. Eligibility and use will also vary by factors such as size and type of practice; physicians in solo practice are much less likely to use electronic health records than physicians in other practice settings. We suggest actions that policy makers can take to lessen disparities and increase the adoption and meaningful use of electronic health records.