Detection of the cross-linked fibrin degradation fragment, D-dimer, in patients at risk for disseminated intravascular coagulation (DIC) is strong evidence for the diagnosis. D-dimer confirms that both thrombin generation and plasmin generation have occurred. Patients at risk for DIC (58) and normal controls (7) were studied. Thirty-three patients had DIC--with fragment D-dimer identified in their serum by immunoblotting. Latex agglutination measurements of fibrin(ogen) degradation products (FDPs) and D-dimer were compared with immunoblotting in the detection of D-dimer. FDP measurement was extremely sensitive but not specific. D-dimer measurement was less sensitive but highly specific. Used in tandem, screening with FDP and confirming with D-dimer, sensitivity and specificity were maximized, rendering a predictive value of a confirmed FDP of 100% in this cohort. D-dimer is a valuable adjunct for the laboratory diagnosis of DIC but is most appropriately used as a confirmatory test for the very sensitive FDP test.