Introduction: The reviews made in 2007 to the current American pharmacopoeia throughout the Western Hemisphere (USP Chapter 797) include a section about handling hazardous drugs as master sterile preparations. In this sense, environmental sampling is recommended to detect traces of dangerous and not contained drugs. It is stated this quality measure should be carried out routinely. Objective: To determine the rate of contamination with cytotoxic agents in the working areas of three hospitals in Colombia. Material and Methods: It was carried out a descriptive, prospective and cross-sectional study. Samples were collected simultaneously from 18 areas. It was evaluated the presence of three drugs that have been historically used as tracers of chemical contamination: Cyclophosphamide, 5-fluorouracil and carboplatin. The surface of preparation areas (biological safety cabinet or isolator CSB-barrier-AB), enlistment areas and the ones of cancer drugs administration including common areas of the central mixing and living areas of oncology drugs administration were evaluated. Results: In the department of nursing and pharmacy exists chemical contamination caused by cytostatic drugs. In nursing pollution was mainly related to carboplatin while in the central mixing area, the most detected document was 5-fluorouracil. The comparison between both departments shows that the highest rate of contamination was found in pharmacy. The most detected active substance was 5-fluorouracil. Conclusion: It is recommended that institutions review the standards for the preparation and administration of hazardous drugs in the light of global standards (USP, ASHP, Isopp) in areas such as politics and the current procedure, engineering controls, cleaning procedures, handling manufacturer's vials, assessment of CSB or AB, training and education of the staff both, in the areas of preparation and administration, use of appropriate PPE, the incidence of recent spills in the pharmacy or preparation area that could raise detection levels and the implementation of CSTD.