In the present paper, three multiparametric coagulation instruments were evaluated with regard to chronometric tests for aPTT (CK-Prest and automated APTT), PT (Recombiplastin and Thromborel), fibrinogen and factors of the prothrombin complex. Analysis of within-run precision and linearity and comparative studies showed the analytical performances of the instruments to differ according to the reagents used and emphasized the difficulty of finding the best compromise between instrument and reagent. On the basis of this study, the mechanical instrument appeared to be more versatile than the optical machines. This conclusion could however be modified after further evaluation of the recent new generation coagulation instruments.