A study has been performed to evaluate the effect of the portacaval shunt on some coagulation tests in the rats. Thrombocytopenia develops, accompanied by a decrease in the total protein and fibrinogen concentrations. Moreover, the Quick time is lengthened, whereas the partial thromboplastin time is not modified. The maximal amplitude and elasticity of the clot, recorded by thrombelastography, appear reduced, and k is lengthened. The results are discussed.