The AA. remark that laboratory diagnosis of intravascular coagulation is a still alive methodological problem. The presence in the flowing blood of certain molecules (fdp) that derive from that alteration of fibrinogen metabolism, that is at the basis of any intravascular coagulation syndrome, can be detected by immunological methods. Paracoagulation tests allow on the contrary to detect fibrin monomers and fibrin degradation products (fdp) that are still clottable (nonenzymatic coagulation). The positivity of these ones constitutes therefore an indirect evidence of the effects of thrombin on fibrinogen and keeps us nearer to the pathogenetic moment which is the real basis of any I.C. syndrome. The AA. make here a parallel between the two principal paracoagulation tests that are S.D.P.S. test according to GUREWICH (1971 [7]) and Ethanol Gelation test according to GODAL (1966 [6]) whose details are given. These two tests were performed in parallel in 589 cases which showed clinical evidence or suspicion of I.C. mostly supported by the further clinical courses of the patients. The two tests are both positive only in 164 cases (27,8%); both non-positive in 109 cases (18,6%); S.D.P.S. test is positive alone in 306 cases (51,9%); Godal's test is positive alone in 10 cases (1,7%). These data, supported by clinical course, allow the AA. to think that S.D.P.S. test is more sensitive than Godal's test. Although the AA. make the hypothesis that S.D.P.S. test may be more sensitive owing to its serial diluitions method that allows it to achieve an optimal ratio between the paracoagulant agent and the molecules which are capable to be clotted (paracoagulated). So they modify Godal's test applying to it too the principle of serial diluitions. The details are given. This new Serial Diluition Ethanol Gelation test is therefore performed in parallel with S.D.P.S. test in 314 cases which showed clinical evidence or suspicion of I.C. mostly supported by further clinical courses of the patients. In this second series of 314 patients the two tests are both positive in 138 cases (43,9%); both non-positive in 33 cases (10,5%); S.D.P.S. test was positive alone in 108 cases (34,3%); S.D.E.G. test was positive alone in 35 cases (11,3%). As we can see in this second series S.D.P.S. test remains more sensitive showing positivities in 246 cases (78,2%) whereas S.D.E.G. test is positive in 173 cases (55,2%). In conclusion the application of serial diluitions also to Ethanol Gelation test increase its sensitivity (from 29,5% to 55,2%), but it does not reach S.D.P.S. test's one. S.D.E.G. test may be really useful in clinics because it gives informations within 10 min but its non-positivity must be supported by the results of S.D.P.S. test which on the contrary gives sure informations only after 24 hours.