BACKGROUND: Numerous studies have examined the relationship between physician practice characteristics and electronic health record (EHR) adoption. Little is known about how payer mix influences physicians' decisions to implement EHR systems. PURPOSE: This study examines how different proportions of Medicare, Medicaid, and privately insured patients in physicians' practices influence EHR adoption. METHODOLOGY: Data from a large-scale survey of physician's use of information technologies in Florida were analyzed. Physicians were categorized based on their responses to questions regarding the proportion of patients in their practice that use Medicare, Medicaid, or private insurance products. The binary dependent variable of interest was EHR adoption among physicians. Adjusted odds ratios (ORs) were computed using logistic regression modeling techniques. The model examined the effect of changes in each payer type on EHR adoption, controlling for various practice characteristics. FINDINGS: Physicians with the highest percentage of Medicaid patients in their practices were significantly less likely to indicate using an EHR system when compared with those in the low-volume Medicaid group (OR = 0.690; 95% confidence interval [CI] = 0.50-0.95). No differences in EHR adoption were detected among physicians in the low, median, and high Medicare volume classifications. Among the private payer classifications, physicians whose practices were in the median group indicated significantly greater EHR use than those with relatively low levels of privately insured patients (OR = 1.62; 95% CI = 1.16-2.27). Those in the high-volume private payer group were also more likely than the low-volume group to have an EHR system, but this trend did not reach statistical significance (OR = 1.44; 95% CI = 0.96-2.16). PRACTICE IMPLICATIONS: Governmental insurance programs are either not influencing or negatively influencing EHR adoption among physicians in Florida. Given the quality and cost benefits associated with EHR use (particularly for health care payers), policymakers should consider strategies to incentivize or reward EHR adoption among doctors who care for Medicare and Medicaid patients. © 2007 Lippincott Williams & Wilkins, Inc.