We measured FDP-D-dimer value in disseminated intravascular coagulation (DIC), pre-DIC (within 7 days before onset of DIC) and suspected DIC (not completely satisfying the DIC criteria). The level of FDP in many patients with pre-DIC was normal, but the level of FDP-D-dimer in most patients with pre-DIC was increased. FDP was markedly increased one day before onset of DIC but FDP-D-dimer was increased 7 days before the onset. FDP was significantly higher in DIC than in pre-DIC, but it was not higher in pre-DIC than in suspected DIC. In patients with hematological malignancies, FDP-D-dimer was statistically higher in DIC than in pre-DIC and in pre-DIC than in suspected DIC, but in non-hematological malignancies, FDP-D-dimer was not significantly different among the 3 groups. The peak increase of FDP-D-dimer was noted at a DIC score of 7 or 8. The correlation of FDP-D-dimer with FDP was better in pre-DIC than in DIC, and the ratio of FDP-D-dimer to FDP was higher in pre-DIC. FDP-D-dimer was not correlated with fibrinopeptide A or B beta 15-42 in pre-DIC. It is speculated that pre-DIC is a hypercoagulable state and FDP-D-dimer may be useful to the diagnosis of pre-DIC.