The fate of human allogeneic aortic valves depends mainly on their histological and immunological condition at the time of transplantation. A screening test making novel use of Alcian Blue was used to determine the integrity of endothelial cells as a prerequisite to their function. The dye uptake into the nucleus was measured quantitatively. The test was used to compare the effect of different storage mediums and temperatures (+4 degrees C, -30 degrees C, -80 degrees C, DMSO, FCS, RPMI, antibiotic solution) on aortic valves of rats. The cell integrity decreased with increasing storage time and higher storage temperature. The cryoprotective agent DMSO had no essential effect on the maintenance of cell integrity.