The purpose of the study is to investigate pathologic conditions which are accompanied by high D-dimer levels (> 500ngr/ml) and towards which the diagnostic approach must be directed. Material and Methods: In 91 hospitalized patients (49 male,42 female) plasma D-dimer levels were measured with ELISA method and the basic disease of each patient were defined after clinical and laboratory testing. Results: None out of 58 patients with low D-dimer levels had VTE, but these levels were not diagnostic for any category of disease (18 infectious, 16 neoplastic, 15 cardiovascular). On the contrary, out of 33 patients with high ddimer concentration levels, 19 (57,5%) had neoplastic desease (p < 0,01) and only 3 (9%) had VTE. Conclusion: Low D-dimer concentrations really exclude VTE, but without being diagnostic for any category of disease On the contrary, high D-dimer levels must guide the diagnostic approach primarily towards subjacent neoplastic disease and secondary towards VTE.