OBJECTIVES: There is no evidence about real medical practice in oncology in Mexico. The objective of this study was to explore current medical practices of Mexican oncologists in the management of five malignancies: breast, non-small cell lung (NSCL), colon, rectum and kidney cancer. METHODS: A specific instrument for these malignancies was designed, validated and applied to Mexican oncologists. Information requested reflects stage-specific treatment and disease management, including surgery and drugs uses, as well as frequency of prescription, discontinuation and factors that determines them in public and private health care institutions, between January-April 2009. RESULTS: 30 oncologists were included: 63.3% from Instituto Mexicano del Seguro Social and 20.0% from Instituto Nacional de Cancerología. 73.3% of all oncologists have public and private practices. Tamoxiphen (adjuvant hormonoterapy) and 5-fluoroacil/epirubicin/cyclophosphamide (adjuvant, neoadjuvant and palliative chemotherapy) are the most frequently drug schemes used in breast cancer, with no differences between public and private practices(p<0.05). At least 85.0% of NSCL cancer cases are diagnosed in IIIA and IV stages; combination chemotherapy (platinum/etoposide) is highly prescribed in NSCL cancer patients undergoing radiotherapy or non-resectable disease. Colon cancer is diagnosed in stages III(58.0%) and IV (14.0%); 20.0% of colon cancer patients undergoes surgery (left or right hemicolectomy). Drug availability and medical guidelines recommendations drive prescription to treat colon cancer. Surgery in rectum cancer is applied at stages IIB, IIIA and IIIB (17.6%, 20.0% and 16.9%, respectively). Rectum cancer presents as non-resectable disease in 60.0% of cases in stage IV. Drugs used to treat metastatic renal cells cancer are interferon-α (80.0%) and sunitinib(19.0%), prescription is driven by drug availability and efficacy, respectively. Discontinuation rate of interferon-α due adverse event was 90.0%. CONCLUSIONS: Knowledge of oncology current medical practice provides a basis for evaluation, as well as supports decision making process and the generation of new strategies for policy makers.