OBJECTIVES: The aim of this study was to measure cancer-related direct expenditures and its determinants, from the third-party payer perspective, for patients newly diagnosed and treated by the National Health System (SUS) from 2000 to 2003. METHODS: We used data from national administrative registries of all patients treated by the SUS. We restricted our sample to patients newly diagnosed between the years 2000 and 2003 with the most prevalent cancers in Brazil (breast, cervix, prostate, lung, colorectal and stomach). Data included expenditures related to chemotherapy and radiotherapy and in-patient care. A generalized linear model with a gamma distribution was used to estimate the determinants of healthcare expenditures. Regressions were performed for the whole sample and then separately by cancer type. RESULTS: A total 180,283 patients were diagnosed with cancer between 2000 and 2003: 38.6% breast, 19.1% cervix, 15.4% prostate, 11.3% lung, 10.8% colorectal and 4.9% stomach cancer. Average monthly expenditures were 315$ and the average follow-up of 18 months. The highest average monthly expenditure was observed for lung cancer (649$) followed by stomach cancer (382$). High discrepancies were observed between states, from 210$ (Maranhão) to 471$ (Roraima). All covariates were significantly related to expenditures. Monthly expenditures decreased with follow-up time and increased with death and presence of metastases. Expenditures were lower among women and decreased continuously with patient’s age, with the lowest expenditures observed among patients older than 80. As compared to cancer in situ, lower expenditures were observed for stage I; by contrast, expenditures were much higher at stage III and IV. Covariates behaved similarly across cancer types, except for the stage of disease. CONCLUSIONS: Average monthly expenditures for cancer treatment in Brazil are relatively low as compared e.g. to estimates for the US. The strong discrepancy between States raises serious concerns about equity and quality.