Background and Goal of Study: Herbs and vitamin supplements have shown to be able to produce coagulation disorders during the perioperative period in patients that take them chronically. We describe a case of a severe hipocoagulability state in a male patient scheduled for a transsphenoidal resection of an hypophyseal tumor who was consuming a natural product containing transfer factors and several types of mushrooms (shiitake and maitake). Materials and Methods: The medical record of the patient was reviewed, including the preoperative coagulation assessment during the anesthetic evaluation, the intraoperative diagnosis and treatment of a severe coagulopathy of unknown origin and its postoperative management. Results: A 62 year old male who was scheduled for a transsphenoidal resection of an hypophyseal tumor with a medical history of hypertension and dyslipidemia developed a severe intraoperative hemorrhage without any vascular injury. A severe coagulation disorder was diagnosed by thromboelastography (figure 1) and was successfully treated with intravenous fluids, blood products and tranexamic acid. The family of the patient was asked for any other medications that were taken before surgery, finding out that transference factors that include shiitake (lentinula edodes) and maitake (grifola frondosa) mushrooms had been taken until the night before.Conclusions/Discussion: Patients consume different natural products, many times without knowing its real compounds, that at times could be harmful. Transfer factor is a popular product that contains a high variety of substances, including lentinula edodes and grifola frondosa, two mushrooms that have shown to have hypocoagulant properties and produce platelet aggregation disfunction. In this case, the team of anesthesiologists was not aware of the chronic use of these substances because this information was not previously provided by the patient in the preoperative anesthetic assessment. We present a case in which L. edodes and G. frondosa are the most reasonable cause of severe hemorrhage and coagulopathy in a patient scheduled for a resection of a tumor of the hypophysis. References Bise, P. Baguel, R. Sanodiya, B. Thakur, G. Prasad, G. Lentinus edodes: A macrofungus with pharmacological activities. Current Medicinal Chemistry. 2010;17: 24119-2430 Hanselin MR, Vande Griend JP, Linnebur SA. INR elevation with maitake extract in combination with warfarin. Ann Pharmacother. 2010;44(1):223-22 Shimada, S. Komamura, K. Kumagai, H. i Sakurai, H. Inhibitory activity of shiitake flavor against platelet aggregation. Biofactors. 2004; 22; 177-179