In 172 patients the thickness of the corneal graft was followed with frequent measurements during the first 14 days after operation. Three different graft thickness time courses were observed. Patients with keratitis, stromal dystrophy and corrosion or mechanical lesion showed a secondary rise in graft thickness on the 6th postoperative day, while patients with keratoconus and those treated with tranexamic acid showed no rise on the 6th day. Patients with Fuchs' dystrophy differed from the other groups in not reaching the maximal thickness until the 3rd postoperative day. The possible correlation of these three time courses with changes in the fibrinolytic system is discussed.