OBJECTIVES: To examine the geographic, age, gender and racial variations in the prevalent population of Lyme disease using U.S Medicaid data.  METHODS: Patients with Lyme disease were identified using International Classification of Disease, 9^th Revision, Clinical Modification (ICD-9-CM) diagnosis code 088.81 from the Medicaid fee-for-service (FFS) population in 2008 and 2009. All patients were required to have 2 years of continuous Medicaid FFS enrollment and no managed care enrollment for any month during the study period. Disease prevalence was stratified by region, state, age, gender and race for all patients. Numbers and percentages of patients in each category were calculated in the descriptive analysis to measure prevalence.  RESULTS: A total of 2,110 patients (0.04%) were diagnosed with Lyme disease in 2008 and 2009. Prevalence was the highest at 0.08% for patients age 40-59 years, compared to those under age 40 (0.05%) and over age 60 (0.02%). Race variation analysis showed the highest Lyme disease prevalence in White patients (0.06%), followed by Asian (0.05%), Native American (0.03%), Hispanic (0.02%) and Black (0.01%).  There was no gender variation in Lyme disease prevalence (0.04%) in the Medicaid FFS population. Prevalence, stratified by U.S. state, was also examined. The highest prevalence rates were found in Connecticut (0.28%), New Hampshire (0.27%), Rhode Island (0.21%), Maryland (0.18%) and Minnesota (0.12%). According to U.S. region, the Northeast (0.10%) had the highest prevalence rate, followed by the Midwest (0.03%), South (0.02%) and West (0.00%).  CONCLUSIONS: Middle-aged patients were shown to have a higher probability for a Lyme disease diagnosis. Stratified by race, White patients were more likely to be diagnosed with Lyme disease compared to all other races. There is also statistical evidence that patients located in the Northeastern U.S. region have a higher risk for a Lyme disease diagnosis.