Euglobulin lysis time is a global test for the study of fibrinolysis. The aim of this study was to evaluate the influence of storage of plasma and euglobulin precipitates on euglobulin lysis time, by testing samples stored in different conditions. In 20 healthy subjects, euglobulin lysis time was measured by (1) euglobulin precipitates prepared within 90 minutes from blood withdrawal (reference euglobulin lysis time); (2) euglobulin precipitates obtained from platelet-poor plasma stored for 24 hours at either -80 degrees C or at -20 degrees C; (3) euglobulin precipitates frozen for 24 hours at either -80 degrees C or at -20 degrees C; (4) euglobulin precipitates dissolved in Owren's buffer and frozen for 24 hours at either -80 degrees C or at -20 degrees C. Euglobulin lysis time measured on euglobulin precipitates dissolved in Owren's buffer and stored at -20 degrees C and at -80 degrees C, and euglobulin lysis time measured on platelet-poor plasma stored at -20 degrees C were significantly longer than the reference euglobulin lysis time (at least P < .05). On the contrary, no changes were observed in euglobulin lysis time measured on platelet-poor plasma stored at -80 degrees C, and on euglobulin precipitates undissolved and stored at -20 degrees C and at -80 degrees C versus reference euglobulin lysis time. The pattern was similar in samples obtained both before and after venous occlusion. These data indicate that the freezing of samples of platelet-poor plasma or euglobulin precipitates at -80 degrees C and of euglobulin precipitates at -20 degrees C makes the simultaneous determination of a large number of samples collected at different times the previous day possible.