Summary. Background: Quantitative bleeding assessment tools (BATs) have been used to describe the severity of the bleeding phenotype in patients with von Willebrand disease. Objectives: To evaluate the clinical usefulness of a BAT for the diagnosis of mild bleeding disorders (MBDs) in previously undiagnosed patients. Methods: We prospectively assessed 215 patients who were consecutively referred for evaluation of bleeding symptoms (n = 71), abnormal laboratory clotting test results (n = 105) or family investigation (n = 39) at two second-level centers. The bleeding history was assessed by a young investigator who administered the BAT instrument, and also by a senior physician who independently evaluated the patient and made the final diagnoses. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were computed for a predefined bleeding score (BS) cut-off (BS of > 3). Receiver operating characteristic curves were used to establish a diagnostic prediction rule. Results: Assuming the prevalence of MBD in the general population to be ∼ 1%, a normal BS (≤ 3) had a very high NPV (99.2%). The PPVs in patients referred for hemostatic or family evaluation at second-level clinics were estimated to be 71.0% and 77.5% (assuming MDB prevalences of 20% and 50%, respectively, in these settings). Measurement of BS in addition to activated partial thromboplastin time significantly increased the diagnostic efficiency of the BAT instrument (NPV of 99.6%). Conclusions: BAT use improves the evaluation of patients with suspected MBD, and we propose its use in a clinical prediction guide based on BAT and activated partial thromboplastin time for the exclusion of patients with suspected MBD in a low-prevalence setting.