SummaryIn vitro whole blood clots were incubated in SK, washed several times in Ringer-solution and then introduced into plasminogen solution. These clots showed marked signs of lysis surpassing those observed in clots that had only been incubated in SK. There was a correlation between the duration of the SK incubation and the clot lysis in the plasminogen solution. We deduce from these findings that SK enters the clots by diffusion and that this process lasts several hours.If SK-incubated clots are placed into an SK-free environment, the SK slowly diffuses out of the thrombi.Even in contact with very slight plasminogen concentrations, SK-incubated clots undergo distinct degrees of lysis.