BACKGROUND: Based on the necessity of detailed information that supports effective strategies to improve cancer outcomes in the different regions of Brazil, the aims of this study were to report demographic aspects and to calculate the prevalence and incidence rates of oncohematological diseases in the region of Vale do Paraíba. METHODS: This is a multicentric prospective study carried out from October 2009 to March 2010. A total of 500 over 19-year-old patients were enrolled. Data such as type of healthcare insurance, gender, age, ethnic classification, place of residence, schooling, income, body mass index, new cases and the period between the first symptoms and a definite diagnosis were collected. The prevalence and incidence rates were calculated according to an estimated number of 1,319,800 inhabitants. RESULTS: The prevalence and incidence rates per 100,000 inhabitants in the period of six months were, respectively: acute myeloid leukemia 1.5 and 0.7; acute lymphoblastic leukemia 0.5 and 0.1; chronic lymphocytic leukemia 2.4 and 0.4; chronic myeloid leukemia 6.2 and 0.8; Hodgkin's lymphoma 2.9 and 0.9; non-Hodgkin lymphoma 9.8 and 4.3; multiple myeloma 5.7 and 0.7; myelodysplastic syndromes 2.1 and 0.2 and myeloproliferative syndromes 5.1 and 0.3. CONCLUSION: Giving the paucity of data in this field of investigation, our data may be useful for comparisons with those of other regions of Brazil and will assist in the implementation of treatment programs of oncohematological diseases in this region.