Introduction. Venous thombosis (VT) is a major complication of cancer. Research over the last decades has shown that primary prophlaxis can reduce DVT, PE and fatal PE. The American Society of Clinical Oncology, the National Comprehensive Cancer Network (NCCN) og the Italian Association of Medical Oncology have developed guideline recommendations for the use of anticoagulation in the prevention and treatment of VT in patients with cancer. Main features of these guidelines are: 1. Patients with cancer should get low molecule weight heparin (LMWH) as prophylaxis prior to surgical procedures or immobilisation.2. In patients with cancer and VT, long-term treatment with LMWH is recommended. 3. In patients with cancer and VT, lifelong treatment should be considered. The purpose of our study was to identify to what extent guidelines in Norwegian hospitals are in accordance with international guidelines. Methods. A questionnaire was sent to all hospitals in Norway, to both medical and surgical departments, requesting their guidelines concerning prophylaxis and treatment of VT in patients with cancer. Results. About two-thirds of the hospitals had general guidelines for both prophylaxis and treatment of VT in patients with cancer. Few hospitals had their own guidelines. Most hospitals treated VT initially with LMWH, and then continued with warfarin. None of the hospitals considered life-long treatment. Our conclusion is that Norwegian cancer pateints do not receive optimal treatment according to international guidelines, and there is room for improvement.