 Consecutive patients with clinically suspected upper extremity deep vein thrombosis UEDVT are potentially eligible for the study. Patients will be categorized as likely or unlikely to have UEDVT based on a clinical decision rule CDR. Patients unlikely for UEDVT based on the CDR and with normal D-dimer levels will not receive anticoagulant treatment and will be followed-up for 3 months. All patients with a likely CDR or patients with an unlikely CDR combined with elevated D-dimer levels will undergo ultrasonography. In case of an indeterminate ultrasonography result, ultrasonography testing will be repeated 3-5 days later. The same applies for patients with a negative ultrasound and the combination of a high probability and elevated D-dimer levels. Anticoagulants will be withheld in all patients for whom UEDVT will be excluded by the initial diagnostic work-up. 