OBJECTIVES: The aim of this study is to determine 1-year direct medical costs of treating patients with Chronic Lymphoid Leukemia (CLL) from the Brazilian Private Healthcare System perspective. METHODS: The Orizon database, an administrative database containing inpatient and outpatient claims to a pool of 102 HMOs representing 34% of the total Private Health System, was reviewed from Jan/2009 to Dec/2012. Eligibility criteria were patients starting CLL (ICD-10 code C911) treatment from Apr/2009 to Dec/2011. Outcome was direct medical costs (DMC) per patient-year, calculated as the sum of the medical claims for each patient included in the analysis, for a maximum period of 12-months or death or loss of follow-up, whichever comes first. DMC was categorized in chemotherapy, hospitalizations, and other outpatient costs. Further analysis was conducted for chemotherapy and hospitalizations. RESULTS: From 735 patients with CLL identified in the database, 164 met eligibility criteria and were included in the analysis, representing a total of 100 patients-years. Total DMC in this population was R$ 16,555,421 (mean cost of R$ 165,827 per patient-year), from which R$ 9,451,124 (57%) are related to chemotherapy, R$ 5,341,862 (32%) to hospitalizations and R$ 1,762,434 (11%) to other outpatient costs. Outpatient laboratory exams accounted for only a small fraction (R$ 176,545, 1%) of DMC, and only one patient had a record of radiotherapy (<1% of DMC).  A total of 326 hospitalizations were identified in 79 (48%) patients, with an average cost of R$ 16,386 ± 29,185 per hospitalization. Chemotherapy drugs accounted for 71% of the total costs with chemotherapy, 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 accounts for almost 90% of the total costs.