a method for determining the existence and the amount of soluble fibrin contained in a specimen fluid is provided . the method includes the steps of precipitating soluble fibrin out of the opaque specimen fluid , aggregating the soluble fibrin precipitates in a limited region of a transparent container so as to render the precipitates optically detectable in the opaque specimen fluid , and optically detecting the precipitates . the amount of soluble fibrin may be determined by measuring the time from the addition of the precipitating regent to the detection of the soluble fibrin precipitates . methods of the present invention allow one to measure soluble fibrin in whole blood , and therefore render the test useful in the operating room under conditions of major surgery and in the presence of severe trauma wherein dic is likely to supervene .