CLSI H59-P: D-dimer is a product of fibrinolysis that is assayed in the blood. It is elevated following intravascular thrombosis, disseminated intravascular coagulation (DIC), and other conditions that can cause fibrin generation. Assay of D-dimer is a useful tool when evaluating patients with possible venous thromboembolism (VTE), the absence of D-dimer being helpful in excluding VTE. Clinical and Laboratory Standards Institute document H59-P--Quantitative D-dimer for the Exclusion of Venous Thromboembolic Disease; Proposed Guideline provides guidance regarding the use of D-dimer in exclusion of VTE including a description of the value of clinical determination of the pretest probability of VTE; the proper collection and handling of the specimen; assays used for D-dimer analysis; determination of the threshold for exclusion of VTE; interpretation of test results; and aspects of regulatory and accreditation requirements. The guideline is provided for use by laboratorians; manufacturers of Ddimer assays; clinicians who use the D-dimer for VTE exclusion; and for accrediting and regulatory agencies.