OBJECTIVES: Cutaneous T-cell lymphoma (CTCL) is a group of lymphoproliferative disorders characterized by neoplastic T-lymphocytes in the skin. The most common form, mycosis fungoides (MF), may impose a substantial financial burden; however, little is known about the actual economic consequences to the U.S. healthcare system. The objective of this study is to estimate health care utilization and cost among these patients by severity. METHODS:  A retrospective cohort study was conducted using the HealthCore Integrated Research Database to identify patients aged 18 and older with a diagnosis of MF-CTCL (ICD-9-CM codes 202.1x, 202.2x) between July 1, 2006 and July 31, 2013. The index date was defined as the first occurrence of MF-CTCL. Patients were required to have at least 6 months of continuous enrollment before and 12 months after the index date. Severe MF-CTCL was defined by systemic therapy use during post-index period. Generalized linear model (GLM) was used to quantify the relationship between MF-CTCL severity and healthcare costs controlling for age, gender, region, health plan, physician specialty, and comorbidities. RESULTS: The final study sample included 493 patients with severe MF-CTCL and 1,488 patients with less severe MF-CTCL. Compared with less severe MF-CTCL patients, severe MF-CTCL patients had, on average, higher all-cause inpatient admissions (1.93 vs. 0.48, p-value < 0.001), emergency room (0.45 vs. 0.22, p-value < 0.0001) and physician office visits (26.6 vs. 15.0, p-value < 0.001), outpatient services (39.0 vs. 29.2, p-value <0.001), and pharmacy scripts (55.1 vs. 25.2, p-value < 0.001). GLM analysis indicates that patients with severe MF-CTCL incurred higher all-cause healthcare costs compared to patients with less severe MF-CTCL (coefficient estimate: 4.19, p-value < 0.0001). CONCLUSIONS:  Patients with severe MF-CTCL had a greater burden of illness, as measured by healthcare costs and utilization, than those with less severe MF-CTCL.