Electronic health records (EHRs) are promising tools to improve quality and efficiency in health care, but data on their adoption rate are limited. We identified surveys on EHR adoption and assessed their quality. Although surveys returned widely different estimates of EHR use, when available information is limited to studies of high or medium quality, national estimates are possible: Through 2005, approximately 23.9 percent of physicians used EHRs in the ambulatory setting, while 5 percent of hospitals used computerized physician order entry. Large gaps in knowledge, including information about EHR use among safety-net providers, pose critical challenges for the development of policies aimed at speeding adoption.