This report concerns our clinical experience with mounted aortic heterograft valves. There were nine patients, four males and five females, ranging in age from 5 to 65 years. The mitral valve was replaced in eight patients (concomitant tricuspid replacement in one), and the aortic valve in one instance. There was one operative death in a child with complete atrioventricularis communis (AV canal). One patient died after Starr valve replacement of a heterograft which had become infected and obstructed four months after implantation. Another patient developed late valve incompetence due to disruption of a cusp, and the heterograft was successfully replaced with a Starr valve. The seven current survivors, six with heterografts, have good valve function. The follow-up period extends from 3 to 13 months.