OBJECTIVES: The aim of this study is to determine 2-year direct medical costs of treating patients with Chronic Lymphocytic Leukemia (CLL) based on the Brazilian Private Healthcare System. METHODS: The Orizon database, an administrative database containing inpatient and outpatient claims from a pool of 102 HMOs representing 34% of the total Private Health System, was reviewed from Jan/2009 to Dec/2014. Eligibility criteria were patients starting CLL (ICD-10 code C911) treatment from Jan/2011 to Dec/2012. Direct medical costs (DMC) per patient-year were calculated as the sum of medical claims for each patient included in the analysis, for a maximum period of 24-months or death or loss of follow-up, whichever came first. DMC was categorized in chemotherapy, hospitalizations, and other outpatient costs. Further analysis was conducted for chemotherapy and hospitalizations. RESULTS: From 535 patients with CLL identified in the database, 175 met eligibility criteria and were included in this analysis, representing a total of 212 patients-years. Total DMC in this population was R$25,597,927 (mean cost of R$120,744 per patient-year), from which R$15,778,157 (62%) were related to chemotherapy, R$5,689,887 (22%) to hospitalizations and R$4,129,883 (16%) to other outpatient costs. Outpatient laboratory exams accounted for only a small fraction (R$989,990, 4%) of DMC.  A total of 265 hospitalizations were identified in 53 (30%) patients, with an average cost of R$21,471 ± 55,938 per hospitalization. Chemotherapy drugs accounted for 68% of the total costs within chemotherapy treatment, the rest divided between other drugs (12%), disposable devices (6%), hospital facility fees (5%) and other costs (6%). CONCLUSIONS: Patients with CLL represent a significant economic burden to private payers. Chemotherapy and hospitalization costs account for about 80% of total costs. Further research will elucidate the cost-effectiveness of novel targeted agents such as ibrutinib, which is administered orally and does not incur costs associated with in-clinic infusions.