OBJECTIVES: The purpose of the study is to calculate the annual health insurance cost of treatment of colorectal cancer at nationwide level in Hungary for the year 2001. METHODS: Data derive from the nationwide database of the Hungarian National Health Insurance Fund Administration (OEP), the only health care financing agency in Hungary. The cost of treatment includes: out-patient care, acute and chronic inpatient care, subsidies of medicines' prices (ATC groups: "L", antineoplastic and immunomodulating agents, "N02", Analgesics and "A04" Antiemetics and antineuseants) and expenditure on disability to work (including sickness-pay). According to standard cost categories direct medical and direct non-medical costs, indirect (productivity) costs are included while informal care and intangible costs are excluded. Disease was identified with the following ICD-10 codes: C18, C19, C20, C21 (Malignant neoplasm of colon, rectosigmoid junction, rectum and anus and anal canal), D01.0, D01.1, D01.2, D01.3, D01.4 (carcinoma in situ), D12 (Benign neoplasm of colon, rectum, anus and anal canal). RESULTS: The results showed the following cost structure. Outpatient care: $1,889,315 or €2,109,102 (5.4 % of total costs), acute inpatient care: $25,994,160 or €29,018,103 (74.7% of total costs), chronic inpatient care: $1,293,650 or €1,444,142 (3.7% of total costs), sickness-pay: $1,293,057 or €1,443,480 (3.7% of total costs), drugs from outpatient care's budget: $4,350,714 or €4,856,839 (12.5 % of total costs). The National Health Insurance Fund Administration (OEP) spent alltogether $34,820,895 or €38,871,666 on colorectal cancer in 2001. Most of the costs (82.8%) derived from malignant neoplasms, 17.0% from benign neoplasms including polyps and 0.2% from in situ cancers. CONCLUSIONS: Colorectal cancer represents a large burden in Hungary. Benign neoplasms including polyps represents an important cost element. Most of the costs come from acute in-patient care.