Homologous dura mater valve was employed in a series of 533 patients in the period between January 1971 and May 1974. The dura mater was sterilized and preserved in 98 percent glycerol solution at room temperature. Important data were the following (1) no significant pressure gradient through the vale at rest; (2) no bacterial endocarditis; (3) two cases of fungal endocarditis; (4) no degeneration or retraction of the leaflets; (5) no thrombus formation in the valve; and (6) no anticoagulants were used in this series.